diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/Swift5ClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/Swift5ClientCodegen.java
index 57325357218..3eb2c0ee650 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/Swift5ClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/Swift5ClientCodegen.java
@@ -34,6 +34,10 @@ import java.io.File;
 import java.util.*;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
+import java.time.OffsetDateTime;
+import java.time.Instant;
+import java.time.temporal.ChronoField;
+import java.util.concurrent.TimeUnit;
 
 import static org.openapitools.codegen.utils.StringUtils.camelize;
 
@@ -620,14 +624,19 @@ public class Swift5ClientCodegen extends DefaultCodegen implements CodegenConfig
                 }
             }
         }
-        if (ModelUtils.isIntegerSchema(p) || ModelUtils.isNumberSchema(p) || ModelUtils.isBooleanSchema(p)) {
-            if (p.getDefault() != null) {
+        if (p.getDefault() != null) {
+            if (ModelUtils.isIntegerSchema(p) || ModelUtils.isNumberSchema(p) || ModelUtils.isBooleanSchema(p)) {
                 return p.getDefault().toString();
-            }
-        } else if (ModelUtils.isStringSchema(p)) {
-            if (p.getDefault() != null) {
+            } else if (ModelUtils.isDateTimeSchema(p)) {
+                // Datetime time stamps in Swift are expressed as Seconds with Microsecond precision.
+                // In Java, we need to be creative to get the Timestamp in Microseconds as a long.
+                Instant instant = ((OffsetDateTime) p.getDefault()).toInstant();
+                long epochMicro = TimeUnit.SECONDS.toMicros(instant.getEpochSecond()) + ((long) instant.get(ChronoField.MICRO_OF_SECOND));
+                return "Date(timeIntervalSince1970: " + String.valueOf(epochMicro) + ".0 / 1_000_000)";
+            } else if (ModelUtils.isStringSchema(p)) {
                 return "\"" + escapeText((String) p.getDefault()) + "\"";
             }
+            // TODO: Handle more cases from `ModelUtils`, such as Date
         }
         return null;
     }
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
index 1af03153596..81020425ad1 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
@@ -12,7 +12,7 @@ public struct AdditionalPropertiesClass: Codable {
     public var mapString: [String: String]?
     public var mapMapString: [String: [String: String]]?
 
-    public init(mapString: [String: String]?, mapMapString: [String: [String: String]]?) {
+    public init(mapString: [String: String]? = nil, mapMapString: [String: [String: String]]? = nil) {
         self.mapString = mapString
         self.mapMapString = mapMapString
     }
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
index 5ed9f31e2a3..c34ac85ac63 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
@@ -12,7 +12,7 @@ public struct Animal: Codable {
     public var className: String
     public var color: String? = "red"
 
-    public init(className: String, color: String?) {
+    public init(className: String, color: String? = nil) {
         self.className = className
         self.color = color
     }
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
index ec270da8907..6ad3d808a97 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
@@ -13,7 +13,7 @@ public struct ApiResponse: Codable {
     public var type: String?
     public var message: String?
 
-    public init(code: Int?, type: String?, message: String?) {
+    public init(code: Int? = nil, type: String? = nil, message: String? = nil) {
         self.code = code
         self.type = type
         self.message = message
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
index 6c252ed475b..6d99f90fdd1 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
@@ -11,7 +11,7 @@ public struct ArrayOfArrayOfNumberOnly: Codable {
 
     public var arrayArrayNumber: [[Double]]?
 
-    public init(arrayArrayNumber: [[Double]]?) {
+    public init(arrayArrayNumber: [[Double]]? = nil) {
         self.arrayArrayNumber = arrayArrayNumber
     }
 
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
index e84eb5d6502..d59c529ef65 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
@@ -11,7 +11,7 @@ public struct ArrayOfNumberOnly: Codable {
 
     public var arrayNumber: [Double]?
 
-    public init(arrayNumber: [Double]?) {
+    public init(arrayNumber: [Double]? = nil) {
         self.arrayNumber = arrayNumber
     }
 
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
index d2140933d18..fdab67b0c59 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
@@ -13,7 +13,7 @@ public struct ArrayTest: Codable {
     public var arrayArrayOfInteger: [[Int64]]?
     public var arrayArrayOfModel: [[ReadOnlyFirst]]?
 
-    public init(arrayOfString: [String]?, arrayArrayOfInteger: [[Int64]]?, arrayArrayOfModel: [[ReadOnlyFirst]]?) {
+    public init(arrayOfString: [String]? = nil, arrayArrayOfInteger: [[Int64]]? = nil, arrayArrayOfModel: [[ReadOnlyFirst]]? = nil) {
         self.arrayOfString = arrayOfString
         self.arrayArrayOfInteger = arrayArrayOfInteger
         self.arrayArrayOfModel = arrayArrayOfModel
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
index d1b3b27616e..a7f8abe9719 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
@@ -17,7 +17,7 @@ public struct Capitalization: Codable {
     /** Name of the pet  */
     public var ATT_NAME: String?
 
-    public init(smallCamel: String?, capitalCamel: String?, smallSnake: String?, capitalSnake: String?, sCAETHFlowPoints: String?, ATT_NAME: String?) {
+    public init(smallCamel: String? = nil, capitalCamel: String? = nil, smallSnake: String? = nil, capitalSnake: String? = nil, sCAETHFlowPoints: String? = nil, ATT_NAME: String? = nil) {
         self.smallCamel = smallCamel
         self.capitalCamel = capitalCamel
         self.smallSnake = smallSnake
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
index 7ab887f3113..884020d1a72 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
@@ -13,7 +13,7 @@ public struct Cat: Codable {
     public var color: String? = "red"
     public var declawed: Bool?
 
-    public init(className: String, color: String?, declawed: Bool?) {
+    public init(className: String, color: String? = nil, declawed: Bool? = nil) {
         self.className = className
         self.color = color
         self.declawed = declawed
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
index a51ad0dffab..c7178efcb16 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
@@ -11,7 +11,7 @@ public struct CatAllOf: Codable {
 
     public var declawed: Bool?
 
-    public init(declawed: Bool?) {
+    public init(declawed: Bool? = nil) {
         self.declawed = declawed
     }
 
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Category.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
index eb8f7e5e197..78bf6826d69 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
@@ -12,7 +12,7 @@ public struct Category: Codable {
     public var id: Int64?
     public var name: String = "default-name"
 
-    public init(id: Int64?, name: String) {
+    public init(id: Int64? = nil, name: String) {
         self.id = id
         self.name = name
     }
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
index e2a7d4427a0..d7299a05856 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
@@ -12,7 +12,7 @@ public struct ClassModel: Codable {
 
     public var _class: String?
 
-    public init(_class: String?) {
+    public init(_class: String? = nil) {
         self._class = _class
     }
 
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Client.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
index 00245ca3728..c8e0b51314d 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
@@ -11,7 +11,7 @@ public struct Client: Codable {
 
     public var client: String?
 
-    public init(client: String?) {
+    public init(client: String? = nil) {
         self.client = client
     }
 
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
index 492c1228008..e7e0efa931e 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
@@ -13,7 +13,7 @@ public struct Dog: Codable {
     public var color: String? = "red"
     public var breed: String?
 
-    public init(className: String, color: String?, breed: String?) {
+    public init(className: String, color: String? = nil, breed: String? = nil) {
         self.className = className
         self.color = color
         self.breed = breed
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
index 7786f8acc5a..1f61ed3c343 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
@@ -11,7 +11,7 @@ public struct DogAllOf: Codable {
 
     public var breed: String?
 
-    public init(breed: String?) {
+    public init(breed: String? = nil) {
         self.breed = breed
     }
 
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
index 9844e7c40e3..10536376ccc 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
@@ -20,7 +20,7 @@ public struct EnumArrays: Codable {
     public var justSymbol: JustSymbol?
     public var arrayEnum: [ArrayEnum]?
 
-    public init(justSymbol: JustSymbol?, arrayEnum: [ArrayEnum]?) {
+    public init(justSymbol: JustSymbol? = nil, arrayEnum: [ArrayEnum]? = nil) {
         self.justSymbol = justSymbol
         self.arrayEnum = arrayEnum
     }
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
index 789f583e1d7..c0d7c84b69d 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
@@ -33,7 +33,7 @@ public struct EnumTest: Codable {
     public var enumNumber: EnumNumber?
     public var outerEnum: OuterEnum?
 
-    public init(enumString: EnumString?, enumStringRequired: EnumStringRequired, enumInteger: EnumInteger?, enumNumber: EnumNumber?, outerEnum: OuterEnum?) {
+    public init(enumString: EnumString? = nil, enumStringRequired: EnumStringRequired, enumInteger: EnumInteger? = nil, enumNumber: EnumNumber? = nil, outerEnum: OuterEnum? = nil) {
         self.enumString = enumString
         self.enumStringRequired = enumStringRequired
         self.enumInteger = enumInteger
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/File.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/File.swift
index abf3ccffc48..54ffb6e70e3 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/File.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/File.swift
@@ -13,7 +13,7 @@ public struct File: Codable {
     /** Test capitalization */
     public var sourceURI: String?
 
-    public init(sourceURI: String?) {
+    public init(sourceURI: String? = nil) {
         self.sourceURI = sourceURI
     }
 
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
index 532f1457939..3d70ffe0a59 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
@@ -12,7 +12,7 @@ public struct FileSchemaTestClass: Codable {
     public var file: File?
     public var files: [File]?
 
-    public init(file: File?, files: [File]?) {
+    public init(file: File? = nil, files: [File]? = nil) {
         self.file = file
         self.files = files
     }
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
index 20bd6d103b3..c934df71b34 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
@@ -23,7 +23,7 @@ public struct FormatTest: Codable {
     public var uuid: UUID?
     public var password: String
 
-    public init(integer: Int?, int32: Int?, int64: Int64?, number: Double, float: Float?, double: Double?, string: String?, byte: Data, binary: URL?, date: Date, dateTime: Date?, uuid: UUID?, password: String) {
+    public init(integer: Int? = nil, int32: Int? = nil, int64: Int64? = nil, number: Double, float: Float? = nil, double: Double? = nil, string: String? = nil, byte: Data, binary: URL? = nil, date: Date, dateTime: Date? = nil, uuid: UUID? = nil, password: String) {
         self.integer = integer
         self.int32 = int32
         self.int64 = int64
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
index 906ddb06fb1..a6d3567e885 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
@@ -12,7 +12,7 @@ public struct HasOnlyReadOnly: Codable {
     public var bar: String?
     public var foo: String?
 
-    public init(bar: String?, foo: String?) {
+    public init(bar: String? = nil, foo: String? = nil) {
         self.bar = bar
         self.foo = foo
     }
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/List.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/List.swift
index fe13d302ccb..6de49531ac1 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/List.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/List.swift
@@ -11,7 +11,7 @@ public struct List: Codable {
 
     public var _123list: String?
 
-    public init(_123list: String?) {
+    public init(_123list: String? = nil) {
         self._123list = _123list
     }
 
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
index 4b6037f378e..a9762da6155 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
@@ -18,7 +18,7 @@ public struct MapTest: Codable {
     public var directMap: [String: Bool]?
     public var indirectMap: StringBooleanMap?
 
-    public init(mapMapOfString: [String: [String: String]]?, mapOfEnumString: [String: String]?, directMap: [String: Bool]?, indirectMap: StringBooleanMap?) {
+    public init(mapMapOfString: [String: [String: String]]? = nil, mapOfEnumString: [String: String]? = nil, directMap: [String: Bool]? = nil, indirectMap: StringBooleanMap? = nil) {
         self.mapMapOfString = mapMapOfString
         self.mapOfEnumString = mapOfEnumString
         self.directMap = directMap
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
index c3deb2f2893..f1d081064b6 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
@@ -13,7 +13,7 @@ public struct MixedPropertiesAndAdditionalPropertiesClass: Codable {
     public var dateTime: Date?
     public var map: [String: Animal]?
 
-    public init(uuid: UUID?, dateTime: Date?, map: [String: Animal]?) {
+    public init(uuid: UUID? = nil, dateTime: Date? = nil, map: [String: Animal]? = nil) {
         self.uuid = uuid
         self.dateTime = dateTime
         self.map = map
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
index b61db7d6e71..6365e8799f7 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
@@ -13,7 +13,7 @@ public struct Model200Response: Codable {
     public var name: Int?
     public var _class: String?
 
-    public init(name: Int?, _class: String?) {
+    public init(name: Int? = nil, _class: String? = nil) {
         self.name = name
         self._class = _class
     }
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Name.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
index 8ab4db44b73..5797209dce3 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
@@ -15,7 +15,7 @@ public struct Name: Codable {
     public var property: String?
     public var _123number: Int?
 
-    public init(name: Int, snakeCase: Int?, property: String?, _123number: Int?) {
+    public init(name: Int, snakeCase: Int? = nil, property: String? = nil, _123number: Int? = nil) {
         self.name = name
         self.snakeCase = snakeCase
         self.property = property
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
index 4d1dafcc2c1..979335c098b 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
@@ -11,7 +11,7 @@ public struct NumberOnly: Codable {
 
     public var justNumber: Double?
 
-    public init(justNumber: Double?) {
+    public init(justNumber: Double? = nil) {
         self.justNumber = justNumber
     }
 
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Order.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
index 40c30cc8609..f1817f7792a 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
@@ -22,7 +22,7 @@ public struct Order: Codable {
     public var status: Status?
     public var complete: Bool? = false
 
-    public init(id: Int64?, petId: Int64?, quantity: Int?, shipDate: Date?, status: Status?, complete: Bool?) {
+    public init(id: Int64? = nil, petId: Int64? = nil, quantity: Int? = nil, shipDate: Date? = nil, status: Status? = nil, complete: Bool? = nil) {
         self.id = id
         self.petId = petId
         self.quantity = quantity
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
index 18c3a024f12..d01e8da2166 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
@@ -13,7 +13,7 @@ public struct OuterComposite: Codable {
     public var myString: String?
     public var myBoolean: Bool?
 
-    public init(myNumber: Double?, myString: String?, myBoolean: Bool?) {
+    public init(myNumber: Double? = nil, myString: String? = nil, myBoolean: Bool? = nil) {
         self.myNumber = myNumber
         self.myString = myString
         self.myBoolean = myBoolean
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
index b9ce0e93325..caea19425d8 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
@@ -22,7 +22,7 @@ public struct Pet: Codable {
     /** pet status in the store */
     public var status: Status?
 
-    public init(id: Int64?, category: Category?, name: String, photoUrls: [String], tags: [Tag]?, status: Status?) {
+    public init(id: Int64? = nil, category: Category? = nil, name: String, photoUrls: [String], tags: [Tag]? = nil, status: Status? = nil) {
         self.id = id
         self.category = category
         self.name = name
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
index 0acd21fd100..f643334038e 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
@@ -12,7 +12,7 @@ public struct ReadOnlyFirst: Codable {
     public var bar: String?
     public var baz: String?
 
-    public init(bar: String?, baz: String?) {
+    public init(bar: String? = nil, baz: String? = nil) {
         self.bar = bar
         self.baz = baz
     }
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Return.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
index c223f993a69..45479e2b0de 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
@@ -12,7 +12,7 @@ public struct Return: Codable {
 
     public var _return: Int?
 
-    public init(_return: Int?) {
+    public init(_return: Int? = nil) {
         self._return = _return
     }
 
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
index 6e8650f76d8..8515496eb27 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
@@ -11,7 +11,7 @@ public struct SpecialModelName: Codable {
 
     public var specialPropertyName: Int64?
 
-    public init(specialPropertyName: Int64?) {
+    public init(specialPropertyName: Int64? = nil) {
         self.specialPropertyName = specialPropertyName
     }
 
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
index 4dd8a9a9f5a..82c02f04b69 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
@@ -12,7 +12,7 @@ public struct Tag: Codable {
     public var id: Int64?
     public var name: String?
 
-    public init(id: Int64?, name: String?) {
+    public init(id: Int64? = nil, name: String? = nil) {
         self.id = id
         self.name = name
     }
diff --git a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/User.swift b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/User.swift
index 79f271ed735..03e2736bd23 100644
--- a/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/User.swift
+++ b/samples/client/petstore/swift5/alamofireLibrary/PetstoreClient/Classes/OpenAPIs/Models/User.swift
@@ -19,7 +19,7 @@ public struct User: Codable {
     /** User Status */
     public var userStatus: Int?
 
-    public init(id: Int64?, username: String?, firstName: String?, lastName: String?, email: String?, password: String?, phone: String?, userStatus: Int?) {
+    public init(id: Int64? = nil, username: String? = nil, firstName: String? = nil, lastName: String? = nil, email: String? = nil, password: String? = nil, phone: String? = nil, userStatus: Int? = nil) {
         self.id = id
         self.username = username
         self.firstName = firstName
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
index 1af03153596..81020425ad1 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
@@ -12,7 +12,7 @@ public struct AdditionalPropertiesClass: Codable {
     public var mapString: [String: String]?
     public var mapMapString: [String: [String: String]]?
 
-    public init(mapString: [String: String]?, mapMapString: [String: [String: String]]?) {
+    public init(mapString: [String: String]? = nil, mapMapString: [String: [String: String]]? = nil) {
         self.mapString = mapString
         self.mapMapString = mapMapString
     }
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
index 5ed9f31e2a3..c34ac85ac63 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
@@ -12,7 +12,7 @@ public struct Animal: Codable {
     public var className: String
     public var color: String? = "red"
 
-    public init(className: String, color: String?) {
+    public init(className: String, color: String? = nil) {
         self.className = className
         self.color = color
     }
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
index ec270da8907..6ad3d808a97 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
@@ -13,7 +13,7 @@ public struct ApiResponse: Codable {
     public var type: String?
     public var message: String?
 
-    public init(code: Int?, type: String?, message: String?) {
+    public init(code: Int? = nil, type: String? = nil, message: String? = nil) {
         self.code = code
         self.type = type
         self.message = message
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
index 6c252ed475b..6d99f90fdd1 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
@@ -11,7 +11,7 @@ public struct ArrayOfArrayOfNumberOnly: Codable {
 
     public var arrayArrayNumber: [[Double]]?
 
-    public init(arrayArrayNumber: [[Double]]?) {
+    public init(arrayArrayNumber: [[Double]]? = nil) {
         self.arrayArrayNumber = arrayArrayNumber
     }
 
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
index e84eb5d6502..d59c529ef65 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
@@ -11,7 +11,7 @@ public struct ArrayOfNumberOnly: Codable {
 
     public var arrayNumber: [Double]?
 
-    public init(arrayNumber: [Double]?) {
+    public init(arrayNumber: [Double]? = nil) {
         self.arrayNumber = arrayNumber
     }
 
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
index d2140933d18..fdab67b0c59 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
@@ -13,7 +13,7 @@ public struct ArrayTest: Codable {
     public var arrayArrayOfInteger: [[Int64]]?
     public var arrayArrayOfModel: [[ReadOnlyFirst]]?
 
-    public init(arrayOfString: [String]?, arrayArrayOfInteger: [[Int64]]?, arrayArrayOfModel: [[ReadOnlyFirst]]?) {
+    public init(arrayOfString: [String]? = nil, arrayArrayOfInteger: [[Int64]]? = nil, arrayArrayOfModel: [[ReadOnlyFirst]]? = nil) {
         self.arrayOfString = arrayOfString
         self.arrayArrayOfInteger = arrayArrayOfInteger
         self.arrayArrayOfModel = arrayArrayOfModel
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
index d1b3b27616e..a7f8abe9719 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
@@ -17,7 +17,7 @@ public struct Capitalization: Codable {
     /** Name of the pet  */
     public var ATT_NAME: String?
 
-    public init(smallCamel: String?, capitalCamel: String?, smallSnake: String?, capitalSnake: String?, sCAETHFlowPoints: String?, ATT_NAME: String?) {
+    public init(smallCamel: String? = nil, capitalCamel: String? = nil, smallSnake: String? = nil, capitalSnake: String? = nil, sCAETHFlowPoints: String? = nil, ATT_NAME: String? = nil) {
         self.smallCamel = smallCamel
         self.capitalCamel = capitalCamel
         self.smallSnake = smallSnake
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
index 7ab887f3113..884020d1a72 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
@@ -13,7 +13,7 @@ public struct Cat: Codable {
     public var color: String? = "red"
     public var declawed: Bool?
 
-    public init(className: String, color: String?, declawed: Bool?) {
+    public init(className: String, color: String? = nil, declawed: Bool? = nil) {
         self.className = className
         self.color = color
         self.declawed = declawed
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
index a51ad0dffab..c7178efcb16 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
@@ -11,7 +11,7 @@ public struct CatAllOf: Codable {
 
     public var declawed: Bool?
 
-    public init(declawed: Bool?) {
+    public init(declawed: Bool? = nil) {
         self.declawed = declawed
     }
 
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Category.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
index eb8f7e5e197..78bf6826d69 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
@@ -12,7 +12,7 @@ public struct Category: Codable {
     public var id: Int64?
     public var name: String = "default-name"
 
-    public init(id: Int64?, name: String) {
+    public init(id: Int64? = nil, name: String) {
         self.id = id
         self.name = name
     }
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
index e2a7d4427a0..d7299a05856 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
@@ -12,7 +12,7 @@ public struct ClassModel: Codable {
 
     public var _class: String?
 
-    public init(_class: String?) {
+    public init(_class: String? = nil) {
         self._class = _class
     }
 
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Client.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
index 00245ca3728..c8e0b51314d 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
@@ -11,7 +11,7 @@ public struct Client: Codable {
 
     public var client: String?
 
-    public init(client: String?) {
+    public init(client: String? = nil) {
         self.client = client
     }
 
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
index 492c1228008..e7e0efa931e 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
@@ -13,7 +13,7 @@ public struct Dog: Codable {
     public var color: String? = "red"
     public var breed: String?
 
-    public init(className: String, color: String?, breed: String?) {
+    public init(className: String, color: String? = nil, breed: String? = nil) {
         self.className = className
         self.color = color
         self.breed = breed
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
index 7786f8acc5a..1f61ed3c343 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
@@ -11,7 +11,7 @@ public struct DogAllOf: Codable {
 
     public var breed: String?
 
-    public init(breed: String?) {
+    public init(breed: String? = nil) {
         self.breed = breed
     }
 
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
index 9844e7c40e3..10536376ccc 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
@@ -20,7 +20,7 @@ public struct EnumArrays: Codable {
     public var justSymbol: JustSymbol?
     public var arrayEnum: [ArrayEnum]?
 
-    public init(justSymbol: JustSymbol?, arrayEnum: [ArrayEnum]?) {
+    public init(justSymbol: JustSymbol? = nil, arrayEnum: [ArrayEnum]? = nil) {
         self.justSymbol = justSymbol
         self.arrayEnum = arrayEnum
     }
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
index 789f583e1d7..c0d7c84b69d 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
@@ -33,7 +33,7 @@ public struct EnumTest: Codable {
     public var enumNumber: EnumNumber?
     public var outerEnum: OuterEnum?
 
-    public init(enumString: EnumString?, enumStringRequired: EnumStringRequired, enumInteger: EnumInteger?, enumNumber: EnumNumber?, outerEnum: OuterEnum?) {
+    public init(enumString: EnumString? = nil, enumStringRequired: EnumStringRequired, enumInteger: EnumInteger? = nil, enumNumber: EnumNumber? = nil, outerEnum: OuterEnum? = nil) {
         self.enumString = enumString
         self.enumStringRequired = enumStringRequired
         self.enumInteger = enumInteger
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/File.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/File.swift
index abf3ccffc48..54ffb6e70e3 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/File.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/File.swift
@@ -13,7 +13,7 @@ public struct File: Codable {
     /** Test capitalization */
     public var sourceURI: String?
 
-    public init(sourceURI: String?) {
+    public init(sourceURI: String? = nil) {
         self.sourceURI = sourceURI
     }
 
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
index 532f1457939..3d70ffe0a59 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
@@ -12,7 +12,7 @@ public struct FileSchemaTestClass: Codable {
     public var file: File?
     public var files: [File]?
 
-    public init(file: File?, files: [File]?) {
+    public init(file: File? = nil, files: [File]? = nil) {
         self.file = file
         self.files = files
     }
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
index 20bd6d103b3..c934df71b34 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
@@ -23,7 +23,7 @@ public struct FormatTest: Codable {
     public var uuid: UUID?
     public var password: String
 
-    public init(integer: Int?, int32: Int?, int64: Int64?, number: Double, float: Float?, double: Double?, string: String?, byte: Data, binary: URL?, date: Date, dateTime: Date?, uuid: UUID?, password: String) {
+    public init(integer: Int? = nil, int32: Int? = nil, int64: Int64? = nil, number: Double, float: Float? = nil, double: Double? = nil, string: String? = nil, byte: Data, binary: URL? = nil, date: Date, dateTime: Date? = nil, uuid: UUID? = nil, password: String) {
         self.integer = integer
         self.int32 = int32
         self.int64 = int64
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
index 906ddb06fb1..a6d3567e885 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
@@ -12,7 +12,7 @@ public struct HasOnlyReadOnly: Codable {
     public var bar: String?
     public var foo: String?
 
-    public init(bar: String?, foo: String?) {
+    public init(bar: String? = nil, foo: String? = nil) {
         self.bar = bar
         self.foo = foo
     }
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/List.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/List.swift
index fe13d302ccb..6de49531ac1 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/List.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/List.swift
@@ -11,7 +11,7 @@ public struct List: Codable {
 
     public var _123list: String?
 
-    public init(_123list: String?) {
+    public init(_123list: String? = nil) {
         self._123list = _123list
     }
 
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
index 4b6037f378e..a9762da6155 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
@@ -18,7 +18,7 @@ public struct MapTest: Codable {
     public var directMap: [String: Bool]?
     public var indirectMap: StringBooleanMap?
 
-    public init(mapMapOfString: [String: [String: String]]?, mapOfEnumString: [String: String]?, directMap: [String: Bool]?, indirectMap: StringBooleanMap?) {
+    public init(mapMapOfString: [String: [String: String]]? = nil, mapOfEnumString: [String: String]? = nil, directMap: [String: Bool]? = nil, indirectMap: StringBooleanMap? = nil) {
         self.mapMapOfString = mapMapOfString
         self.mapOfEnumString = mapOfEnumString
         self.directMap = directMap
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
index c3deb2f2893..f1d081064b6 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
@@ -13,7 +13,7 @@ public struct MixedPropertiesAndAdditionalPropertiesClass: Codable {
     public var dateTime: Date?
     public var map: [String: Animal]?
 
-    public init(uuid: UUID?, dateTime: Date?, map: [String: Animal]?) {
+    public init(uuid: UUID? = nil, dateTime: Date? = nil, map: [String: Animal]? = nil) {
         self.uuid = uuid
         self.dateTime = dateTime
         self.map = map
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
index b61db7d6e71..6365e8799f7 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
@@ -13,7 +13,7 @@ public struct Model200Response: Codable {
     public var name: Int?
     public var _class: String?
 
-    public init(name: Int?, _class: String?) {
+    public init(name: Int? = nil, _class: String? = nil) {
         self.name = name
         self._class = _class
     }
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Name.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
index 8ab4db44b73..5797209dce3 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
@@ -15,7 +15,7 @@ public struct Name: Codable {
     public var property: String?
     public var _123number: Int?
 
-    public init(name: Int, snakeCase: Int?, property: String?, _123number: Int?) {
+    public init(name: Int, snakeCase: Int? = nil, property: String? = nil, _123number: Int? = nil) {
         self.name = name
         self.snakeCase = snakeCase
         self.property = property
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
index 4d1dafcc2c1..979335c098b 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
@@ -11,7 +11,7 @@ public struct NumberOnly: Codable {
 
     public var justNumber: Double?
 
-    public init(justNumber: Double?) {
+    public init(justNumber: Double? = nil) {
         self.justNumber = justNumber
     }
 
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Order.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
index 40c30cc8609..f1817f7792a 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
@@ -22,7 +22,7 @@ public struct Order: Codable {
     public var status: Status?
     public var complete: Bool? = false
 
-    public init(id: Int64?, petId: Int64?, quantity: Int?, shipDate: Date?, status: Status?, complete: Bool?) {
+    public init(id: Int64? = nil, petId: Int64? = nil, quantity: Int? = nil, shipDate: Date? = nil, status: Status? = nil, complete: Bool? = nil) {
         self.id = id
         self.petId = petId
         self.quantity = quantity
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
index 18c3a024f12..d01e8da2166 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
@@ -13,7 +13,7 @@ public struct OuterComposite: Codable {
     public var myString: String?
     public var myBoolean: Bool?
 
-    public init(myNumber: Double?, myString: String?, myBoolean: Bool?) {
+    public init(myNumber: Double? = nil, myString: String? = nil, myBoolean: Bool? = nil) {
         self.myNumber = myNumber
         self.myString = myString
         self.myBoolean = myBoolean
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
index b9ce0e93325..caea19425d8 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
@@ -22,7 +22,7 @@ public struct Pet: Codable {
     /** pet status in the store */
     public var status: Status?
 
-    public init(id: Int64?, category: Category?, name: String, photoUrls: [String], tags: [Tag]?, status: Status?) {
+    public init(id: Int64? = nil, category: Category? = nil, name: String, photoUrls: [String], tags: [Tag]? = nil, status: Status? = nil) {
         self.id = id
         self.category = category
         self.name = name
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
index 0acd21fd100..f643334038e 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
@@ -12,7 +12,7 @@ public struct ReadOnlyFirst: Codable {
     public var bar: String?
     public var baz: String?
 
-    public init(bar: String?, baz: String?) {
+    public init(bar: String? = nil, baz: String? = nil) {
         self.bar = bar
         self.baz = baz
     }
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Return.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
index c223f993a69..45479e2b0de 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
@@ -12,7 +12,7 @@ public struct Return: Codable {
 
     public var _return: Int?
 
-    public init(_return: Int?) {
+    public init(_return: Int? = nil) {
         self._return = _return
     }
 
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
index 6e8650f76d8..8515496eb27 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
@@ -11,7 +11,7 @@ public struct SpecialModelName: Codable {
 
     public var specialPropertyName: Int64?
 
-    public init(specialPropertyName: Int64?) {
+    public init(specialPropertyName: Int64? = nil) {
         self.specialPropertyName = specialPropertyName
     }
 
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
index 4dd8a9a9f5a..82c02f04b69 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
@@ -12,7 +12,7 @@ public struct Tag: Codable {
     public var id: Int64?
     public var name: String?
 
-    public init(id: Int64?, name: String?) {
+    public init(id: Int64? = nil, name: String? = nil) {
         self.id = id
         self.name = name
     }
diff --git a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/User.swift b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/User.swift
index 79f271ed735..03e2736bd23 100644
--- a/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/User.swift
+++ b/samples/client/petstore/swift5/combineLibrary/PetstoreClient/Classes/OpenAPIs/Models/User.swift
@@ -19,7 +19,7 @@ public struct User: Codable {
     /** User Status */
     public var userStatus: Int?
 
-    public init(id: Int64?, username: String?, firstName: String?, lastName: String?, email: String?, password: String?, phone: String?, userStatus: Int?) {
+    public init(id: Int64? = nil, username: String? = nil, firstName: String? = nil, lastName: String? = nil, email: String? = nil, password: String? = nil, phone: String? = nil, userStatus: Int? = nil) {
         self.id = id
         self.username = username
         self.firstName = firstName
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
index 1af03153596..81020425ad1 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
@@ -12,7 +12,7 @@ public struct AdditionalPropertiesClass: Codable {
     public var mapString: [String: String]?
     public var mapMapString: [String: [String: String]]?
 
-    public init(mapString: [String: String]?, mapMapString: [String: [String: String]]?) {
+    public init(mapString: [String: String]? = nil, mapMapString: [String: [String: String]]? = nil) {
         self.mapString = mapString
         self.mapMapString = mapMapString
     }
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
index 5ed9f31e2a3..c34ac85ac63 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
@@ -12,7 +12,7 @@ public struct Animal: Codable {
     public var className: String
     public var color: String? = "red"
 
-    public init(className: String, color: String?) {
+    public init(className: String, color: String? = nil) {
         self.className = className
         self.color = color
     }
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
index ec270da8907..6ad3d808a97 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
@@ -13,7 +13,7 @@ public struct ApiResponse: Codable {
     public var type: String?
     public var message: String?
 
-    public init(code: Int?, type: String?, message: String?) {
+    public init(code: Int? = nil, type: String? = nil, message: String? = nil) {
         self.code = code
         self.type = type
         self.message = message
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
index 6c252ed475b..6d99f90fdd1 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
@@ -11,7 +11,7 @@ public struct ArrayOfArrayOfNumberOnly: Codable {
 
     public var arrayArrayNumber: [[Double]]?
 
-    public init(arrayArrayNumber: [[Double]]?) {
+    public init(arrayArrayNumber: [[Double]]? = nil) {
         self.arrayArrayNumber = arrayArrayNumber
     }
 
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
index e84eb5d6502..d59c529ef65 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
@@ -11,7 +11,7 @@ public struct ArrayOfNumberOnly: Codable {
 
     public var arrayNumber: [Double]?
 
-    public init(arrayNumber: [Double]?) {
+    public init(arrayNumber: [Double]? = nil) {
         self.arrayNumber = arrayNumber
     }
 
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
index d2140933d18..fdab67b0c59 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
@@ -13,7 +13,7 @@ public struct ArrayTest: Codable {
     public var arrayArrayOfInteger: [[Int64]]?
     public var arrayArrayOfModel: [[ReadOnlyFirst]]?
 
-    public init(arrayOfString: [String]?, arrayArrayOfInteger: [[Int64]]?, arrayArrayOfModel: [[ReadOnlyFirst]]?) {
+    public init(arrayOfString: [String]? = nil, arrayArrayOfInteger: [[Int64]]? = nil, arrayArrayOfModel: [[ReadOnlyFirst]]? = nil) {
         self.arrayOfString = arrayOfString
         self.arrayArrayOfInteger = arrayArrayOfInteger
         self.arrayArrayOfModel = arrayArrayOfModel
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
index d1b3b27616e..a7f8abe9719 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
@@ -17,7 +17,7 @@ public struct Capitalization: Codable {
     /** Name of the pet  */
     public var ATT_NAME: String?
 
-    public init(smallCamel: String?, capitalCamel: String?, smallSnake: String?, capitalSnake: String?, sCAETHFlowPoints: String?, ATT_NAME: String?) {
+    public init(smallCamel: String? = nil, capitalCamel: String? = nil, smallSnake: String? = nil, capitalSnake: String? = nil, sCAETHFlowPoints: String? = nil, ATT_NAME: String? = nil) {
         self.smallCamel = smallCamel
         self.capitalCamel = capitalCamel
         self.smallSnake = smallSnake
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
index 7ab887f3113..884020d1a72 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
@@ -13,7 +13,7 @@ public struct Cat: Codable {
     public var color: String? = "red"
     public var declawed: Bool?
 
-    public init(className: String, color: String?, declawed: Bool?) {
+    public init(className: String, color: String? = nil, declawed: Bool? = nil) {
         self.className = className
         self.color = color
         self.declawed = declawed
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
index a51ad0dffab..c7178efcb16 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
@@ -11,7 +11,7 @@ public struct CatAllOf: Codable {
 
     public var declawed: Bool?
 
-    public init(declawed: Bool?) {
+    public init(declawed: Bool? = nil) {
         self.declawed = declawed
     }
 
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Category.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
index eb8f7e5e197..78bf6826d69 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
@@ -12,7 +12,7 @@ public struct Category: Codable {
     public var id: Int64?
     public var name: String = "default-name"
 
-    public init(id: Int64?, name: String) {
+    public init(id: Int64? = nil, name: String) {
         self.id = id
         self.name = name
     }
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
index e2a7d4427a0..d7299a05856 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
@@ -12,7 +12,7 @@ public struct ClassModel: Codable {
 
     public var _class: String?
 
-    public init(_class: String?) {
+    public init(_class: String? = nil) {
         self._class = _class
     }
 
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Client.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
index 00245ca3728..c8e0b51314d 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
@@ -11,7 +11,7 @@ public struct Client: Codable {
 
     public var client: String?
 
-    public init(client: String?) {
+    public init(client: String? = nil) {
         self.client = client
     }
 
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
index 492c1228008..e7e0efa931e 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
@@ -13,7 +13,7 @@ public struct Dog: Codable {
     public var color: String? = "red"
     public var breed: String?
 
-    public init(className: String, color: String?, breed: String?) {
+    public init(className: String, color: String? = nil, breed: String? = nil) {
         self.className = className
         self.color = color
         self.breed = breed
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
index 7786f8acc5a..1f61ed3c343 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
@@ -11,7 +11,7 @@ public struct DogAllOf: Codable {
 
     public var breed: String?
 
-    public init(breed: String?) {
+    public init(breed: String? = nil) {
         self.breed = breed
     }
 
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
index 9844e7c40e3..10536376ccc 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
@@ -20,7 +20,7 @@ public struct EnumArrays: Codable {
     public var justSymbol: JustSymbol?
     public var arrayEnum: [ArrayEnum]?
 
-    public init(justSymbol: JustSymbol?, arrayEnum: [ArrayEnum]?) {
+    public init(justSymbol: JustSymbol? = nil, arrayEnum: [ArrayEnum]? = nil) {
         self.justSymbol = justSymbol
         self.arrayEnum = arrayEnum
     }
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
index 789f583e1d7..c0d7c84b69d 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
@@ -33,7 +33,7 @@ public struct EnumTest: Codable {
     public var enumNumber: EnumNumber?
     public var outerEnum: OuterEnum?
 
-    public init(enumString: EnumString?, enumStringRequired: EnumStringRequired, enumInteger: EnumInteger?, enumNumber: EnumNumber?, outerEnum: OuterEnum?) {
+    public init(enumString: EnumString? = nil, enumStringRequired: EnumStringRequired, enumInteger: EnumInteger? = nil, enumNumber: EnumNumber? = nil, outerEnum: OuterEnum? = nil) {
         self.enumString = enumString
         self.enumStringRequired = enumStringRequired
         self.enumInteger = enumInteger
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/File.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/File.swift
index abf3ccffc48..54ffb6e70e3 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/File.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/File.swift
@@ -13,7 +13,7 @@ public struct File: Codable {
     /** Test capitalization */
     public var sourceURI: String?
 
-    public init(sourceURI: String?) {
+    public init(sourceURI: String? = nil) {
         self.sourceURI = sourceURI
     }
 
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
index 532f1457939..3d70ffe0a59 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
@@ -12,7 +12,7 @@ public struct FileSchemaTestClass: Codable {
     public var file: File?
     public var files: [File]?
 
-    public init(file: File?, files: [File]?) {
+    public init(file: File? = nil, files: [File]? = nil) {
         self.file = file
         self.files = files
     }
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
index 20bd6d103b3..c934df71b34 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
@@ -23,7 +23,7 @@ public struct FormatTest: Codable {
     public var uuid: UUID?
     public var password: String
 
-    public init(integer: Int?, int32: Int?, int64: Int64?, number: Double, float: Float?, double: Double?, string: String?, byte: Data, binary: URL?, date: Date, dateTime: Date?, uuid: UUID?, password: String) {
+    public init(integer: Int? = nil, int32: Int? = nil, int64: Int64? = nil, number: Double, float: Float? = nil, double: Double? = nil, string: String? = nil, byte: Data, binary: URL? = nil, date: Date, dateTime: Date? = nil, uuid: UUID? = nil, password: String) {
         self.integer = integer
         self.int32 = int32
         self.int64 = int64
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
index 906ddb06fb1..a6d3567e885 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
@@ -12,7 +12,7 @@ public struct HasOnlyReadOnly: Codable {
     public var bar: String?
     public var foo: String?
 
-    public init(bar: String?, foo: String?) {
+    public init(bar: String? = nil, foo: String? = nil) {
         self.bar = bar
         self.foo = foo
     }
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/List.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/List.swift
index fe13d302ccb..6de49531ac1 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/List.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/List.swift
@@ -11,7 +11,7 @@ public struct List: Codable {
 
     public var _123list: String?
 
-    public init(_123list: String?) {
+    public init(_123list: String? = nil) {
         self._123list = _123list
     }
 
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
index 4b6037f378e..a9762da6155 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
@@ -18,7 +18,7 @@ public struct MapTest: Codable {
     public var directMap: [String: Bool]?
     public var indirectMap: StringBooleanMap?
 
-    public init(mapMapOfString: [String: [String: String]]?, mapOfEnumString: [String: String]?, directMap: [String: Bool]?, indirectMap: StringBooleanMap?) {
+    public init(mapMapOfString: [String: [String: String]]? = nil, mapOfEnumString: [String: String]? = nil, directMap: [String: Bool]? = nil, indirectMap: StringBooleanMap? = nil) {
         self.mapMapOfString = mapMapOfString
         self.mapOfEnumString = mapOfEnumString
         self.directMap = directMap
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
index c3deb2f2893..f1d081064b6 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
@@ -13,7 +13,7 @@ public struct MixedPropertiesAndAdditionalPropertiesClass: Codable {
     public var dateTime: Date?
     public var map: [String: Animal]?
 
-    public init(uuid: UUID?, dateTime: Date?, map: [String: Animal]?) {
+    public init(uuid: UUID? = nil, dateTime: Date? = nil, map: [String: Animal]? = nil) {
         self.uuid = uuid
         self.dateTime = dateTime
         self.map = map
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
index b61db7d6e71..6365e8799f7 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
@@ -13,7 +13,7 @@ public struct Model200Response: Codable {
     public var name: Int?
     public var _class: String?
 
-    public init(name: Int?, _class: String?) {
+    public init(name: Int? = nil, _class: String? = nil) {
         self.name = name
         self._class = _class
     }
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Name.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
index 8ab4db44b73..5797209dce3 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
@@ -15,7 +15,7 @@ public struct Name: Codable {
     public var property: String?
     public var _123number: Int?
 
-    public init(name: Int, snakeCase: Int?, property: String?, _123number: Int?) {
+    public init(name: Int, snakeCase: Int? = nil, property: String? = nil, _123number: Int? = nil) {
         self.name = name
         self.snakeCase = snakeCase
         self.property = property
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
index 4d1dafcc2c1..979335c098b 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
@@ -11,7 +11,7 @@ public struct NumberOnly: Codable {
 
     public var justNumber: Double?
 
-    public init(justNumber: Double?) {
+    public init(justNumber: Double? = nil) {
         self.justNumber = justNumber
     }
 
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Order.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
index 40c30cc8609..f1817f7792a 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
@@ -22,7 +22,7 @@ public struct Order: Codable {
     public var status: Status?
     public var complete: Bool? = false
 
-    public init(id: Int64?, petId: Int64?, quantity: Int?, shipDate: Date?, status: Status?, complete: Bool?) {
+    public init(id: Int64? = nil, petId: Int64? = nil, quantity: Int? = nil, shipDate: Date? = nil, status: Status? = nil, complete: Bool? = nil) {
         self.id = id
         self.petId = petId
         self.quantity = quantity
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
index 18c3a024f12..d01e8da2166 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
@@ -13,7 +13,7 @@ public struct OuterComposite: Codable {
     public var myString: String?
     public var myBoolean: Bool?
 
-    public init(myNumber: Double?, myString: String?, myBoolean: Bool?) {
+    public init(myNumber: Double? = nil, myString: String? = nil, myBoolean: Bool? = nil) {
         self.myNumber = myNumber
         self.myString = myString
         self.myBoolean = myBoolean
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
index b9ce0e93325..caea19425d8 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
@@ -22,7 +22,7 @@ public struct Pet: Codable {
     /** pet status in the store */
     public var status: Status?
 
-    public init(id: Int64?, category: Category?, name: String, photoUrls: [String], tags: [Tag]?, status: Status?) {
+    public init(id: Int64? = nil, category: Category? = nil, name: String, photoUrls: [String], tags: [Tag]? = nil, status: Status? = nil) {
         self.id = id
         self.category = category
         self.name = name
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
index 0acd21fd100..f643334038e 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
@@ -12,7 +12,7 @@ public struct ReadOnlyFirst: Codable {
     public var bar: String?
     public var baz: String?
 
-    public init(bar: String?, baz: String?) {
+    public init(bar: String? = nil, baz: String? = nil) {
         self.bar = bar
         self.baz = baz
     }
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Return.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
index c223f993a69..45479e2b0de 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
@@ -12,7 +12,7 @@ public struct Return: Codable {
 
     public var _return: Int?
 
-    public init(_return: Int?) {
+    public init(_return: Int? = nil) {
         self._return = _return
     }
 
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
index 6e8650f76d8..8515496eb27 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
@@ -11,7 +11,7 @@ public struct SpecialModelName: Codable {
 
     public var specialPropertyName: Int64?
 
-    public init(specialPropertyName: Int64?) {
+    public init(specialPropertyName: Int64? = nil) {
         self.specialPropertyName = specialPropertyName
     }
 
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
index 4dd8a9a9f5a..82c02f04b69 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
@@ -12,7 +12,7 @@ public struct Tag: Codable {
     public var id: Int64?
     public var name: String?
 
-    public init(id: Int64?, name: String?) {
+    public init(id: Int64? = nil, name: String? = nil) {
         self.id = id
         self.name = name
     }
diff --git a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/User.swift b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/User.swift
index 79f271ed735..03e2736bd23 100644
--- a/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/User.swift
+++ b/samples/client/petstore/swift5/default/PetstoreClient/Classes/OpenAPIs/Models/User.swift
@@ -19,7 +19,7 @@ public struct User: Codable {
     /** User Status */
     public var userStatus: Int?
 
-    public init(id: Int64?, username: String?, firstName: String?, lastName: String?, email: String?, password: String?, phone: String?, userStatus: Int?) {
+    public init(id: Int64? = nil, username: String? = nil, firstName: String? = nil, lastName: String? = nil, email: String? = nil, password: String? = nil, phone: String? = nil, userStatus: Int? = nil) {
         self.id = id
         self.username = username
         self.firstName = firstName
diff --git a/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift b/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
index e74820fd28a..0d028ae6dfa 100644
--- a/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
+++ b/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
@@ -14,7 +14,7 @@ public struct ApiResponse: Codable {
     public var type: String?
     public var message: String?
 
-    public init(code: Int?, type: String?, message: String?) {
+    public init(code: Int? = nil, type: String? = nil, message: String? = nil) {
         self.code = code
         self.type = type
         self.message = message
diff --git a/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/Category.swift b/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
index fec18cc7a6c..cce4425f2e0 100644
--- a/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
+++ b/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
@@ -13,7 +13,7 @@ public struct Category: Codable {
     public var id: Int64?
     public var name: String?
 
-    public init(id: Int64?, name: String?) {
+    public init(id: Int64? = nil, name: String? = nil) {
         self.id = id
         self.name = name
     }
diff --git a/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/InlineObject.swift b/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/InlineObject.swift
index ac5216fe687..105118c79fb 100644
--- a/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/InlineObject.swift
+++ b/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/InlineObject.swift
@@ -14,7 +14,7 @@ public struct InlineObject: Codable {
     /** Updated status of the pet */
     public var status: String?
 
-    public init(name: String?, status: String?) {
+    public init(name: String? = nil, status: String? = nil) {
         self.name = name
         self.status = status
     }
diff --git a/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/InlineObject1.swift b/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/InlineObject1.swift
index 1c2fd3255dd..b19120339cd 100644
--- a/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/InlineObject1.swift
+++ b/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/InlineObject1.swift
@@ -14,7 +14,7 @@ public struct InlineObject1: Codable {
     /** file to upload */
     public var file: URL?
 
-    public init(additionalMetadata: String?, file: URL?) {
+    public init(additionalMetadata: String? = nil, file: URL? = nil) {
         self.additionalMetadata = additionalMetadata
         self.file = file
     }
diff --git a/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/Order.swift b/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
index 1fa6995d1c7..f3d9fcb15fb 100644
--- a/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
+++ b/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
@@ -24,7 +24,7 @@ public struct Order: Codable {
     public var status: Status?
     public var complete: Bool? = false
 
-    public init(id: Int64?, petId: Int64?, quantity: Int?, shipDate: Date?, status: Status?, complete: Bool?) {
+    public init(id: Int64? = nil, petId: Int64? = nil, quantity: Int? = nil, shipDate: Date? = nil, status: Status? = nil, complete: Bool? = nil) {
         self.id = id
         self.petId = petId
         self.quantity = quantity
diff --git a/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift b/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
index 622f2c9bd43..cb69946cd9f 100644
--- a/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
+++ b/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
@@ -25,7 +25,7 @@ public struct Pet: Codable {
     /** pet status in the store */
     public var status: Status?
 
-    public init(id: Int64?, category: Category?, name: String?, photoUrls: [String], tags: [Tag]?, status: Status?) {
+    public init(id: Int64? = nil, category: Category? = nil, name: String?, photoUrls: [String], tags: [Tag]? = nil, status: Status? = nil) {
         self.id = id
         self.category = category
         self.name = name
diff --git a/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift b/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
index 98a78982e59..a8aec56825c 100644
--- a/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
+++ b/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
@@ -13,7 +13,7 @@ public struct Tag: Codable {
     public var id: Int64?
     public var name: String?
 
-    public init(id: Int64?, name: String?) {
+    public init(id: Int64? = nil, name: String? = nil) {
         self.id = id
         self.name = name
     }
diff --git a/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/User.swift b/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/User.swift
index 4e42f6f2859..a9856d0c250 100644
--- a/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/User.swift
+++ b/samples/client/petstore/swift5/deprecated/PetstoreClient/Classes/OpenAPIs/Models/User.swift
@@ -20,7 +20,7 @@ public struct User: Codable {
     /** User Status */
     public var userStatus: Int?
 
-    public init(id: Int64?, username: String?, firstName: String?, lastName: String?, email: String?, password: String?, phone: String?, userStatus: Int?) {
+    public init(id: Int64? = nil, username: String? = nil, firstName: String? = nil, lastName: String? = nil, email: String? = nil, password: String? = nil, phone: String? = nil, userStatus: Int? = nil) {
         self.id = id
         self.username = username
         self.firstName = firstName
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
index b4d5ae6faf9..09e6ebc4b49 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
@@ -12,7 +12,7 @@ internal struct AdditionalPropertiesClass: Codable {
     internal var mapString: [String: String]?
     internal var mapMapString: [String: [String: String]]?
 
-    internal init(mapString: [String: String]?, mapMapString: [String: [String: String]]?) {
+    internal init(mapString: [String: String]? = nil, mapMapString: [String: [String: String]]? = nil) {
         self.mapString = mapString
         self.mapMapString = mapMapString
     }
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
index ada7f86de50..1bafc8ada6f 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
@@ -12,7 +12,7 @@ internal struct Animal: Codable {
     internal var className: String
     internal var color: String? = "red"
 
-    internal init(className: String, color: String?) {
+    internal init(className: String, color: String? = nil) {
         self.className = className
         self.color = color
     }
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
index b60d8999b4b..fc77d48b36b 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
@@ -13,7 +13,7 @@ internal struct ApiResponse: Codable {
     internal var type: String?
     internal var message: String?
 
-    internal init(code: Int?, type: String?, message: String?) {
+    internal init(code: Int? = nil, type: String? = nil, message: String? = nil) {
         self.code = code
         self.type = type
         self.message = message
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
index 67371b816b3..439da58f805 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
@@ -11,7 +11,7 @@ internal struct ArrayOfArrayOfNumberOnly: Codable {
 
     internal var arrayArrayNumber: [[Double]]?
 
-    internal init(arrayArrayNumber: [[Double]]?) {
+    internal init(arrayArrayNumber: [[Double]]? = nil) {
         self.arrayArrayNumber = arrayArrayNumber
     }
 
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
index 2c7047eac4b..30de538bcdd 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
@@ -11,7 +11,7 @@ internal struct ArrayOfNumberOnly: Codable {
 
     internal var arrayNumber: [Double]?
 
-    internal init(arrayNumber: [Double]?) {
+    internal init(arrayNumber: [Double]? = nil) {
         self.arrayNumber = arrayNumber
     }
 
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
index 9c3a3a9f5e1..eaa2955731d 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
@@ -13,7 +13,7 @@ internal struct ArrayTest: Codable {
     internal var arrayArrayOfInteger: [[Int64]]?
     internal var arrayArrayOfModel: [[ReadOnlyFirst]]?
 
-    internal init(arrayOfString: [String]?, arrayArrayOfInteger: [[Int64]]?, arrayArrayOfModel: [[ReadOnlyFirst]]?) {
+    internal init(arrayOfString: [String]? = nil, arrayArrayOfInteger: [[Int64]]? = nil, arrayArrayOfModel: [[ReadOnlyFirst]]? = nil) {
         self.arrayOfString = arrayOfString
         self.arrayArrayOfInteger = arrayArrayOfInteger
         self.arrayArrayOfModel = arrayArrayOfModel
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
index 965ec5aefba..2671163a05c 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
@@ -17,7 +17,7 @@ internal struct Capitalization: Codable {
     /** Name of the pet  */
     internal var ATT_NAME: String?
 
-    internal init(smallCamel: String?, capitalCamel: String?, smallSnake: String?, capitalSnake: String?, sCAETHFlowPoints: String?, ATT_NAME: String?) {
+    internal init(smallCamel: String? = nil, capitalCamel: String? = nil, smallSnake: String? = nil, capitalSnake: String? = nil, sCAETHFlowPoints: String? = nil, ATT_NAME: String? = nil) {
         self.smallCamel = smallCamel
         self.capitalCamel = capitalCamel
         self.smallSnake = smallSnake
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
index 8a603dee5f1..0959d1301da 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
@@ -13,7 +13,7 @@ internal struct Cat: Codable {
     internal var color: String? = "red"
     internal var declawed: Bool?
 
-    internal init(className: String, color: String?, declawed: Bool?) {
+    internal init(className: String, color: String? = nil, declawed: Bool? = nil) {
         self.className = className
         self.color = color
         self.declawed = declawed
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
index 45b7dbb26dc..83f120f746b 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
@@ -11,7 +11,7 @@ internal struct CatAllOf: Codable {
 
     internal var declawed: Bool?
 
-    internal init(declawed: Bool?) {
+    internal init(declawed: Bool? = nil) {
         self.declawed = declawed
     }
 
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Category.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
index 849bf788dfb..5910c7e82ce 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
@@ -12,7 +12,7 @@ internal struct Category: Codable {
     internal var id: Int64?
     internal var name: String = "default-name"
 
-    internal init(id: Int64?, name: String) {
+    internal init(id: Int64? = nil, name: String) {
         self.id = id
         self.name = name
     }
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
index 0f1bc19fe59..7fc865ea3d4 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
@@ -12,7 +12,7 @@ internal struct ClassModel: Codable {
 
     internal var _class: String?
 
-    internal init(_class: String?) {
+    internal init(_class: String? = nil) {
         self._class = _class
     }
 
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Client.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
index ddee836043f..59724d8cdb6 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
@@ -11,7 +11,7 @@ internal struct Client: Codable {
 
     internal var client: String?
 
-    internal init(client: String?) {
+    internal init(client: String? = nil) {
         self.client = client
     }
 
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
index 6b5250de4a4..2af5a26ba54 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
@@ -13,7 +13,7 @@ internal struct Dog: Codable {
     internal var color: String? = "red"
     internal var breed: String?
 
-    internal init(className: String, color: String?, breed: String?) {
+    internal init(className: String, color: String? = nil, breed: String? = nil) {
         self.className = className
         self.color = color
         self.breed = breed
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
index ef3ff7f1d78..11b13c686cd 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
@@ -11,7 +11,7 @@ internal struct DogAllOf: Codable {
 
     internal var breed: String?
 
-    internal init(breed: String?) {
+    internal init(breed: String? = nil) {
         self.breed = breed
     }
 
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
index bb9f64cfb43..71a14c425db 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
@@ -20,7 +20,7 @@ internal struct EnumArrays: Codable {
     internal var justSymbol: JustSymbol?
     internal var arrayEnum: [ArrayEnum]?
 
-    internal init(justSymbol: JustSymbol?, arrayEnum: [ArrayEnum]?) {
+    internal init(justSymbol: JustSymbol? = nil, arrayEnum: [ArrayEnum]? = nil) {
         self.justSymbol = justSymbol
         self.arrayEnum = arrayEnum
     }
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
index 421aa5436b0..7fc50b1d9ad 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
@@ -33,7 +33,7 @@ internal struct EnumTest: Codable {
     internal var enumNumber: EnumNumber?
     internal var outerEnum: OuterEnum?
 
-    internal init(enumString: EnumString?, enumStringRequired: EnumStringRequired, enumInteger: EnumInteger?, enumNumber: EnumNumber?, outerEnum: OuterEnum?) {
+    internal init(enumString: EnumString? = nil, enumStringRequired: EnumStringRequired, enumInteger: EnumInteger? = nil, enumNumber: EnumNumber? = nil, outerEnum: OuterEnum? = nil) {
         self.enumString = enumString
         self.enumStringRequired = enumStringRequired
         self.enumInteger = enumInteger
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/File.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/File.swift
index 632402fb9e0..9eec1bbe3ce 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/File.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/File.swift
@@ -13,7 +13,7 @@ internal struct File: Codable {
     /** Test capitalization */
     internal var sourceURI: String?
 
-    internal init(sourceURI: String?) {
+    internal init(sourceURI: String? = nil) {
         self.sourceURI = sourceURI
     }
 
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
index e478e6c4b7d..1561814449a 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
@@ -12,7 +12,7 @@ internal struct FileSchemaTestClass: Codable {
     internal var file: File?
     internal var files: [File]?
 
-    internal init(file: File?, files: [File]?) {
+    internal init(file: File? = nil, files: [File]? = nil) {
         self.file = file
         self.files = files
     }
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
index 23395c93b56..1fdef5a2da1 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
@@ -23,7 +23,7 @@ internal struct FormatTest: Codable {
     internal var uuid: UUID?
     internal var password: String
 
-    internal init(integer: Int?, int32: Int?, int64: Int64?, number: Double, float: Float?, double: Double?, string: String?, byte: Data, binary: URL?, date: Date, dateTime: Date?, uuid: UUID?, password: String) {
+    internal init(integer: Int? = nil, int32: Int? = nil, int64: Int64? = nil, number: Double, float: Float? = nil, double: Double? = nil, string: String? = nil, byte: Data, binary: URL? = nil, date: Date, dateTime: Date? = nil, uuid: UUID? = nil, password: String) {
         self.integer = integer
         self.int32 = int32
         self.int64 = int64
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
index 831963ba2ed..d32e73c16ce 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
@@ -12,7 +12,7 @@ internal struct HasOnlyReadOnly: Codable {
     internal var bar: String?
     internal var foo: String?
 
-    internal init(bar: String?, foo: String?) {
+    internal init(bar: String? = nil, foo: String? = nil) {
         self.bar = bar
         self.foo = foo
     }
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/List.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/List.swift
index c5960de2151..ecbe69589ca 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/List.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/List.swift
@@ -11,7 +11,7 @@ internal struct List: Codable {
 
     internal var _123list: String?
 
-    internal init(_123list: String?) {
+    internal init(_123list: String? = nil) {
         self._123list = _123list
     }
 
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
index db4f8f436aa..def9e790c87 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
@@ -18,7 +18,7 @@ internal struct MapTest: Codable {
     internal var directMap: [String: Bool]?
     internal var indirectMap: StringBooleanMap?
 
-    internal init(mapMapOfString: [String: [String: String]]?, mapOfEnumString: [String: String]?, directMap: [String: Bool]?, indirectMap: StringBooleanMap?) {
+    internal init(mapMapOfString: [String: [String: String]]? = nil, mapOfEnumString: [String: String]? = nil, directMap: [String: Bool]? = nil, indirectMap: StringBooleanMap? = nil) {
         self.mapMapOfString = mapMapOfString
         self.mapOfEnumString = mapOfEnumString
         self.directMap = directMap
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
index c71bb9256b0..2051ee9029a 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
@@ -13,7 +13,7 @@ internal struct MixedPropertiesAndAdditionalPropertiesClass: Codable {
     internal var dateTime: Date?
     internal var map: [String: Animal]?
 
-    internal init(uuid: UUID?, dateTime: Date?, map: [String: Animal]?) {
+    internal init(uuid: UUID? = nil, dateTime: Date? = nil, map: [String: Animal]? = nil) {
         self.uuid = uuid
         self.dateTime = dateTime
         self.map = map
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
index 5d31a885f75..4a8f2335576 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
@@ -13,7 +13,7 @@ internal struct Model200Response: Codable {
     internal var name: Int?
     internal var _class: String?
 
-    internal init(name: Int?, _class: String?) {
+    internal init(name: Int? = nil, _class: String? = nil) {
         self.name = name
         self._class = _class
     }
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Name.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
index 2aa8fb1524c..68c69c938f2 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
@@ -15,7 +15,7 @@ internal struct Name: Codable {
     internal var property: String?
     internal var _123number: Int?
 
-    internal init(name: Int, snakeCase: Int?, property: String?, _123number: Int?) {
+    internal init(name: Int, snakeCase: Int? = nil, property: String? = nil, _123number: Int? = nil) {
         self.name = name
         self.snakeCase = snakeCase
         self.property = property
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
index 49d73706e39..e85566c5faf 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
@@ -11,7 +11,7 @@ internal struct NumberOnly: Codable {
 
     internal var justNumber: Double?
 
-    internal init(justNumber: Double?) {
+    internal init(justNumber: Double? = nil) {
         self.justNumber = justNumber
     }
 
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Order.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
index dcefb40efa2..e29eae4ef78 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
@@ -22,7 +22,7 @@ internal struct Order: Codable {
     internal var status: Status?
     internal var complete: Bool? = false
 
-    internal init(id: Int64?, petId: Int64?, quantity: Int?, shipDate: Date?, status: Status?, complete: Bool?) {
+    internal init(id: Int64? = nil, petId: Int64? = nil, quantity: Int? = nil, shipDate: Date? = nil, status: Status? = nil, complete: Bool? = nil) {
         self.id = id
         self.petId = petId
         self.quantity = quantity
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
index c61c2c4a462..26fde8ac39a 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
@@ -13,7 +13,7 @@ internal struct OuterComposite: Codable {
     internal var myString: String?
     internal var myBoolean: Bool?
 
-    internal init(myNumber: Double?, myString: String?, myBoolean: Bool?) {
+    internal init(myNumber: Double? = nil, myString: String? = nil, myBoolean: Bool? = nil) {
         self.myNumber = myNumber
         self.myString = myString
         self.myBoolean = myBoolean
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
index b71700544d0..6d0dee3d3d3 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
@@ -22,7 +22,7 @@ internal struct Pet: Codable {
     /** pet status in the store */
     internal var status: Status?
 
-    internal init(id: Int64?, category: Category?, name: String, photoUrls: [String], tags: [Tag]?, status: Status?) {
+    internal init(id: Int64? = nil, category: Category? = nil, name: String, photoUrls: [String], tags: [Tag]? = nil, status: Status? = nil) {
         self.id = id
         self.category = category
         self.name = name
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
index d02c6cc5fd9..c60dbfc8466 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
@@ -12,7 +12,7 @@ internal struct ReadOnlyFirst: Codable {
     internal var bar: String?
     internal var baz: String?
 
-    internal init(bar: String?, baz: String?) {
+    internal init(bar: String? = nil, baz: String? = nil) {
         self.bar = bar
         self.baz = baz
     }
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Return.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
index 95a18b571ad..f1ca7ea2b28 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
@@ -12,7 +12,7 @@ internal struct Return: Codable {
 
     internal var _return: Int?
 
-    internal init(_return: Int?) {
+    internal init(_return: Int? = nil) {
         self._return = _return
     }
 
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
index b6ac3651f0e..e48bb1e791b 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
@@ -11,7 +11,7 @@ internal struct SpecialModelName: Codable {
 
     internal var specialPropertyName: Int64?
 
-    internal init(specialPropertyName: Int64?) {
+    internal init(specialPropertyName: Int64? = nil) {
         self.specialPropertyName = specialPropertyName
     }
 
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
index 1e4de951fb2..9ef32df964c 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
@@ -12,7 +12,7 @@ internal struct Tag: Codable {
     internal var id: Int64?
     internal var name: String?
 
-    internal init(id: Int64?, name: String?) {
+    internal init(id: Int64? = nil, name: String? = nil) {
         self.id = id
         self.name = name
     }
diff --git a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/User.swift b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/User.swift
index ada8a7f82d9..bd8c6e5d683 100644
--- a/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/User.swift
+++ b/samples/client/petstore/swift5/nonPublicApi/PetstoreClient/Classes/OpenAPIs/Models/User.swift
@@ -19,7 +19,7 @@ internal struct User: Codable {
     /** User Status */
     internal var userStatus: Int?
 
-    internal init(id: Int64?, username: String?, firstName: String?, lastName: String?, email: String?, password: String?, phone: String?, userStatus: Int?) {
+    internal init(id: Int64? = nil, username: String? = nil, firstName: String? = nil, lastName: String? = nil, email: String? = nil, password: String? = nil, phone: String? = nil, userStatus: Int? = nil) {
         self.id = id
         self.username = username
         self.firstName = firstName
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
index e184d769179..620f778bcc9 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
@@ -12,7 +12,7 @@ import Foundation
     public var mapString: [String: String]?
     public var mapMapString: [String: [String: String]]?
 
-    public init(mapString: [String: String]?, mapMapString: [String: [String: String]]?) {
+    public init(mapString: [String: String]? = nil, mapMapString: [String: [String: String]]? = nil) {
         self.mapString = mapString
         self.mapMapString = mapMapString
     }
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
index 88152934da2..e870a6023c6 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
@@ -12,7 +12,7 @@ import Foundation
     public var _className: String
     public var color: String? = "red"
 
-    public init(_className: String, color: String?) {
+    public init(_className: String, color: String? = nil) {
         self._className = _className
         self.color = color
     }
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
index d0fcd436885..38334c39011 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
@@ -18,7 +18,7 @@ import Foundation
     public var type: String?
     public var message: String?
 
-    public init(code: Int?, type: String?, message: String?) {
+    public init(code: Int? = nil, type: String? = nil, message: String? = nil) {
         self.code = code
         self.type = type
         self.message = message
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
index 9e3f3aba246..8ef73e96f01 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
@@ -11,7 +11,7 @@ import Foundation
 
     public var arrayArrayNumber: [[Double]]?
 
-    public init(arrayArrayNumber: [[Double]]?) {
+    public init(arrayArrayNumber: [[Double]]? = nil) {
         self.arrayArrayNumber = arrayArrayNumber
     }
 
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
index d287cc1563a..dd95bb5be0c 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
@@ -11,7 +11,7 @@ import Foundation
 
     public var arrayNumber: [Double]?
 
-    public init(arrayNumber: [Double]?) {
+    public init(arrayNumber: [Double]? = nil) {
         self.arrayNumber = arrayNumber
     }
 
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
index dcc3e9c3dd5..7b93023aa35 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
@@ -13,7 +13,7 @@ import Foundation
     public var arrayArrayOfInteger: [[Int64]]?
     public var arrayArrayOfModel: [[ReadOnlyFirst]]?
 
-    public init(arrayOfString: [String]?, arrayArrayOfInteger: [[Int64]]?, arrayArrayOfModel: [[ReadOnlyFirst]]?) {
+    public init(arrayOfString: [String]? = nil, arrayArrayOfInteger: [[Int64]]? = nil, arrayArrayOfModel: [[ReadOnlyFirst]]? = nil) {
         self.arrayOfString = arrayOfString
         self.arrayArrayOfInteger = arrayArrayOfInteger
         self.arrayArrayOfModel = arrayArrayOfModel
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
index 80a5667445f..2b42d0b4586 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
@@ -17,7 +17,7 @@ import Foundation
     /** Name of the pet  */
     public var ATT_NAME: String?
 
-    public init(smallCamel: String?, capitalCamel: String?, smallSnake: String?, capitalSnake: String?, sCAETHFlowPoints: String?, ATT_NAME: String?) {
+    public init(smallCamel: String? = nil, capitalCamel: String? = nil, smallSnake: String? = nil, capitalSnake: String? = nil, sCAETHFlowPoints: String? = nil, ATT_NAME: String? = nil) {
         self.smallCamel = smallCamel
         self.capitalCamel = capitalCamel
         self.smallSnake = smallSnake
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
index 78de5a909f5..4368187bfba 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
@@ -18,7 +18,7 @@ import Foundation
         }
     }
 
-    public init(_className: String, color: String?, declawed: Bool?) {
+    public init(_className: String, color: String? = nil, declawed: Bool? = nil) {
         self._className = _className
         self.color = color
         self.declawed = declawed
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
index ef8cec45aff..6a4b10e996c 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
@@ -16,7 +16,7 @@ import Foundation
         }
     }
 
-    public init(declawed: Bool?) {
+    public init(declawed: Bool? = nil) {
         self.declawed = declawed
     }
 
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Category.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
index 0610c10c982..b5b8b86b56b 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
@@ -17,7 +17,7 @@ import Foundation
     }
     public var name: String = "default-name"
 
-    public init(_id: Int64?, name: String) {
+    public init(_id: Int64? = nil, name: String) {
         self._id = _id
         self.name = name
     }
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
index 4197ffcaed6..2005900e6b5 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
@@ -13,7 +13,7 @@ import Foundation
 
     public var _class: String?
 
-    public init(_class: String?) {
+    public init(_class: String? = nil) {
         self._class = _class
     }
 
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Client.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
index 517dbbba2ec..4c1efdd4140 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
@@ -11,7 +11,7 @@ import Foundation
 
     public var client: String?
 
-    public init(client: String?) {
+    public init(client: String? = nil) {
         self.client = client
     }
 
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
index 37733cd1f3b..a55d537695d 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
@@ -13,7 +13,7 @@ import Foundation
     public var color: String? = "red"
     public var breed: String?
 
-    public init(_className: String, color: String?, breed: String?) {
+    public init(_className: String, color: String? = nil, breed: String? = nil) {
         self._className = _className
         self.color = color
         self.breed = breed
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
index 73fd1822725..41c63007088 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
@@ -11,7 +11,7 @@ import Foundation
 
     public var breed: String?
 
-    public init(breed: String?) {
+    public init(breed: String? = nil) {
         self.breed = breed
     }
 
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
index 034a58c6c0e..6e8c9d0f9ab 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
@@ -20,7 +20,7 @@ import Foundation
     public var justSymbol: JustSymbol?
     public var arrayEnum: [ArrayEnum]?
 
-    public init(justSymbol: JustSymbol?, arrayEnum: [ArrayEnum]?) {
+    public init(justSymbol: JustSymbol? = nil, arrayEnum: [ArrayEnum]? = nil) {
         self.justSymbol = justSymbol
         self.arrayEnum = arrayEnum
     }
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
index ce3a0300609..dd3e83306c3 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
@@ -33,7 +33,7 @@ import Foundation
     public var enumNumber: EnumNumber?
     public var outerEnum: OuterEnum?
 
-    public init(enumString: EnumString?, enumStringRequired: EnumStringRequired, enumInteger: EnumInteger?, enumNumber: EnumNumber?, outerEnum: OuterEnum?) {
+    public init(enumString: EnumString? = nil, enumStringRequired: EnumStringRequired, enumInteger: EnumInteger? = nil, enumNumber: EnumNumber? = nil, outerEnum: OuterEnum? = nil) {
         self.enumString = enumString
         self.enumStringRequired = enumStringRequired
         self.enumInteger = enumInteger
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/File.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/File.swift
index 7a320c177d3..4c6ab7da6c8 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/File.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/File.swift
@@ -14,7 +14,7 @@ import Foundation
     /** Test capitalization */
     public var sourceURI: String?
 
-    public init(sourceURI: String?) {
+    public init(sourceURI: String? = nil) {
         self.sourceURI = sourceURI
     }
 
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
index a6437b4fe90..be5963357fd 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
@@ -12,7 +12,7 @@ import Foundation
     public var file: File?
     public var files: [File]?
 
-    public init(file: File?, files: [File]?) {
+    public init(file: File? = nil, files: [File]? = nil) {
         self.file = file
         self.files = files
     }
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
index df2c46d3757..84f419103a4 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
@@ -48,7 +48,7 @@ import Foundation
     public var uuid: UUID?
     public var password: String
 
-    public init(integer: Int?, int32: Int?, int64: Int64?, number: Double, float: Float?, double: Double?, string: String?, byte: Data, binary: URL?, date: Date, dateTime: Date?, uuid: UUID?, password: String) {
+    public init(integer: Int? = nil, int32: Int? = nil, int64: Int64? = nil, number: Double, float: Float? = nil, double: Double? = nil, string: String? = nil, byte: Data, binary: URL? = nil, date: Date, dateTime: Date? = nil, uuid: UUID? = nil, password: String) {
         self.integer = integer
         self.int32 = int32
         self.int64 = int64
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
index b9f5b39117d..7ca91927af7 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
@@ -12,7 +12,7 @@ import Foundation
     public var bar: String?
     public var foo: String?
 
-    public init(bar: String?, foo: String?) {
+    public init(bar: String? = nil, foo: String? = nil) {
         self.bar = bar
         self.foo = foo
     }
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/List.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/List.swift
index 826dc9e27f2..7a977c19c7c 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/List.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/List.swift
@@ -11,7 +11,7 @@ import Foundation
 
     public var _123list: String?
 
-    public init(_123list: String?) {
+    public init(_123list: String? = nil) {
         self._123list = _123list
     }
 
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
index 2b97660b80e..ba407e3ea25 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
@@ -18,7 +18,7 @@ import Foundation
     public var directMap: [String: Bool]?
     public var indirectMap: StringBooleanMap?
 
-    public init(mapMapOfString: [String: [String: String]]?, mapOfEnumString: [String: String]?, directMap: [String: Bool]?, indirectMap: StringBooleanMap?) {
+    public init(mapMapOfString: [String: [String: String]]? = nil, mapOfEnumString: [String: String]? = nil, directMap: [String: Bool]? = nil, indirectMap: StringBooleanMap? = nil) {
         self.mapMapOfString = mapMapOfString
         self.mapOfEnumString = mapOfEnumString
         self.directMap = directMap
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
index e10adad0a7e..bd503cb36fc 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
@@ -13,7 +13,7 @@ import Foundation
     public var dateTime: Date?
     public var map: [String: Animal]?
 
-    public init(uuid: UUID?, dateTime: Date?, map: [String: Animal]?) {
+    public init(uuid: UUID? = nil, dateTime: Date? = nil, map: [String: Animal]? = nil) {
         self.uuid = uuid
         self.dateTime = dateTime
         self.map = map
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
index 1c5410f61dd..6814183719d 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
@@ -19,7 +19,7 @@ import Foundation
     }
     public var _class: String?
 
-    public init(name: Int?, _class: String?) {
+    public init(name: Int? = nil, _class: String? = nil) {
         self.name = name
         self._class = _class
     }
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Name.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
index 06f8a2f81a3..6ecf78e3885 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
@@ -26,7 +26,7 @@ import Foundation
         }
     }
 
-    public init(name: Int, snakeCase: Int?, property: String?, _123number: Int?) {
+    public init(name: Int, snakeCase: Int? = nil, property: String? = nil, _123number: Int? = nil) {
         self.name = name
         self.snakeCase = snakeCase
         self.property = property
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
index 3bd9859378d..40fa7365d0a 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
@@ -11,7 +11,7 @@ import Foundation
 
     public var justNumber: Double?
 
-    public init(justNumber: Double?) {
+    public init(justNumber: Double? = nil) {
         self.justNumber = justNumber
     }
 
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Order.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
index 586a4c2d55a..1281a50c1dc 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
@@ -42,7 +42,7 @@ import Foundation
         }
     }
 
-    public init(_id: Int64?, petId: Int64?, quantity: Int?, shipDate: Date?, status: Status?, complete: Bool?) {
+    public init(_id: Int64? = nil, petId: Int64? = nil, quantity: Int? = nil, shipDate: Date? = nil, status: Status? = nil, complete: Bool? = nil) {
         self._id = _id
         self.petId = petId
         self.quantity = quantity
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
index 434111678de..9238070c2cb 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
@@ -18,7 +18,7 @@ import Foundation
         }
     }
 
-    public init(myNumber: Double?, myString: String?, myBoolean: Bool?) {
+    public init(myNumber: Double? = nil, myString: String? = nil, myBoolean: Bool? = nil) {
         self.myNumber = myNumber
         self.myString = myString
         self.myBoolean = myBoolean
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
index d84079a2b48..e17ada14c42 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
@@ -27,7 +27,7 @@ import Foundation
     /** pet status in the store */
     public var status: Status?
 
-    public init(_id: Int64?, category: Category?, name: String, photoUrls: [String], tags: [Tag]?, status: Status?) {
+    public init(_id: Int64? = nil, category: Category? = nil, name: String, photoUrls: [String], tags: [Tag]? = nil, status: Status? = nil) {
         self._id = _id
         self.category = category
         self.name = name
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
index d1252433b2d..c16846f4ac1 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
@@ -12,7 +12,7 @@ import Foundation
     public var bar: String?
     public var baz: String?
 
-    public init(bar: String?, baz: String?) {
+    public init(bar: String? = nil, baz: String? = nil) {
         self.bar = bar
         self.baz = baz
     }
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Return.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
index 4b10ac18cf0..9f886e6d507 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
@@ -18,7 +18,7 @@ import Foundation
         }
     }
 
-    public init(_return: Int?) {
+    public init(_return: Int? = nil) {
         self._return = _return
     }
 
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
index 85e33352531..41b2bf459ef 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
@@ -16,7 +16,7 @@ import Foundation
         }
     }
 
-    public init(specialPropertyName: Int64?) {
+    public init(specialPropertyName: Int64? = nil) {
         self.specialPropertyName = specialPropertyName
     }
 
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
index 88583be7f5d..fc02765d30e 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
@@ -17,7 +17,7 @@ import Foundation
     }
     public var name: String?
 
-    public init(_id: Int64?, name: String?) {
+    public init(_id: Int64? = nil, name: String? = nil) {
         self._id = _id
         self.name = name
     }
diff --git a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/User.swift b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/User.swift
index 7dc3cc5954d..5b983150797 100644
--- a/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/User.swift
+++ b/samples/client/petstore/swift5/objcCompatible/PetstoreClient/Classes/OpenAPIs/Models/User.swift
@@ -29,7 +29,7 @@ import Foundation
         }
     }
 
-    public init(_id: Int64?, username: String?, firstName: String?, lastName: String?, email: String?, password: String?, phone: String?, userStatus: Int?) {
+    public init(_id: Int64? = nil, username: String? = nil, firstName: String? = nil, lastName: String? = nil, email: String? = nil, password: String? = nil, phone: String? = nil, userStatus: Int? = nil) {
         self._id = _id
         self.username = username
         self.firstName = firstName
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
index 1af03153596..81020425ad1 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
@@ -12,7 +12,7 @@ public struct AdditionalPropertiesClass: Codable {
     public var mapString: [String: String]?
     public var mapMapString: [String: [String: String]]?
 
-    public init(mapString: [String: String]?, mapMapString: [String: [String: String]]?) {
+    public init(mapString: [String: String]? = nil, mapMapString: [String: [String: String]]? = nil) {
         self.mapString = mapString
         self.mapMapString = mapMapString
     }
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
index 5ed9f31e2a3..c34ac85ac63 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
@@ -12,7 +12,7 @@ public struct Animal: Codable {
     public var className: String
     public var color: String? = "red"
 
-    public init(className: String, color: String?) {
+    public init(className: String, color: String? = nil) {
         self.className = className
         self.color = color
     }
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
index ec270da8907..6ad3d808a97 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
@@ -13,7 +13,7 @@ public struct ApiResponse: Codable {
     public var type: String?
     public var message: String?
 
-    public init(code: Int?, type: String?, message: String?) {
+    public init(code: Int? = nil, type: String? = nil, message: String? = nil) {
         self.code = code
         self.type = type
         self.message = message
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
index 6c252ed475b..6d99f90fdd1 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
@@ -11,7 +11,7 @@ public struct ArrayOfArrayOfNumberOnly: Codable {
 
     public var arrayArrayNumber: [[Double]]?
 
-    public init(arrayArrayNumber: [[Double]]?) {
+    public init(arrayArrayNumber: [[Double]]? = nil) {
         self.arrayArrayNumber = arrayArrayNumber
     }
 
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
index e84eb5d6502..d59c529ef65 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
@@ -11,7 +11,7 @@ public struct ArrayOfNumberOnly: Codable {
 
     public var arrayNumber: [Double]?
 
-    public init(arrayNumber: [Double]?) {
+    public init(arrayNumber: [Double]? = nil) {
         self.arrayNumber = arrayNumber
     }
 
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
index d2140933d18..fdab67b0c59 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
@@ -13,7 +13,7 @@ public struct ArrayTest: Codable {
     public var arrayArrayOfInteger: [[Int64]]?
     public var arrayArrayOfModel: [[ReadOnlyFirst]]?
 
-    public init(arrayOfString: [String]?, arrayArrayOfInteger: [[Int64]]?, arrayArrayOfModel: [[ReadOnlyFirst]]?) {
+    public init(arrayOfString: [String]? = nil, arrayArrayOfInteger: [[Int64]]? = nil, arrayArrayOfModel: [[ReadOnlyFirst]]? = nil) {
         self.arrayOfString = arrayOfString
         self.arrayArrayOfInteger = arrayArrayOfInteger
         self.arrayArrayOfModel = arrayArrayOfModel
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
index d1b3b27616e..a7f8abe9719 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
@@ -17,7 +17,7 @@ public struct Capitalization: Codable {
     /** Name of the pet  */
     public var ATT_NAME: String?
 
-    public init(smallCamel: String?, capitalCamel: String?, smallSnake: String?, capitalSnake: String?, sCAETHFlowPoints: String?, ATT_NAME: String?) {
+    public init(smallCamel: String? = nil, capitalCamel: String? = nil, smallSnake: String? = nil, capitalSnake: String? = nil, sCAETHFlowPoints: String? = nil, ATT_NAME: String? = nil) {
         self.smallCamel = smallCamel
         self.capitalCamel = capitalCamel
         self.smallSnake = smallSnake
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
index 7ab887f3113..884020d1a72 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
@@ -13,7 +13,7 @@ public struct Cat: Codable {
     public var color: String? = "red"
     public var declawed: Bool?
 
-    public init(className: String, color: String?, declawed: Bool?) {
+    public init(className: String, color: String? = nil, declawed: Bool? = nil) {
         self.className = className
         self.color = color
         self.declawed = declawed
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
index a51ad0dffab..c7178efcb16 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
@@ -11,7 +11,7 @@ public struct CatAllOf: Codable {
 
     public var declawed: Bool?
 
-    public init(declawed: Bool?) {
+    public init(declawed: Bool? = nil) {
         self.declawed = declawed
     }
 
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Category.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
index eb8f7e5e197..78bf6826d69 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
@@ -12,7 +12,7 @@ public struct Category: Codable {
     public var id: Int64?
     public var name: String = "default-name"
 
-    public init(id: Int64?, name: String) {
+    public init(id: Int64? = nil, name: String) {
         self.id = id
         self.name = name
     }
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
index e2a7d4427a0..d7299a05856 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
@@ -12,7 +12,7 @@ public struct ClassModel: Codable {
 
     public var _class: String?
 
-    public init(_class: String?) {
+    public init(_class: String? = nil) {
         self._class = _class
     }
 
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Client.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
index 00245ca3728..c8e0b51314d 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
@@ -11,7 +11,7 @@ public struct Client: Codable {
 
     public var client: String?
 
-    public init(client: String?) {
+    public init(client: String? = nil) {
         self.client = client
     }
 
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
index 492c1228008..e7e0efa931e 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
@@ -13,7 +13,7 @@ public struct Dog: Codable {
     public var color: String? = "red"
     public var breed: String?
 
-    public init(className: String, color: String?, breed: String?) {
+    public init(className: String, color: String? = nil, breed: String? = nil) {
         self.className = className
         self.color = color
         self.breed = breed
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
index 7786f8acc5a..1f61ed3c343 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
@@ -11,7 +11,7 @@ public struct DogAllOf: Codable {
 
     public var breed: String?
 
-    public init(breed: String?) {
+    public init(breed: String? = nil) {
         self.breed = breed
     }
 
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
index 9844e7c40e3..10536376ccc 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
@@ -20,7 +20,7 @@ public struct EnumArrays: Codable {
     public var justSymbol: JustSymbol?
     public var arrayEnum: [ArrayEnum]?
 
-    public init(justSymbol: JustSymbol?, arrayEnum: [ArrayEnum]?) {
+    public init(justSymbol: JustSymbol? = nil, arrayEnum: [ArrayEnum]? = nil) {
         self.justSymbol = justSymbol
         self.arrayEnum = arrayEnum
     }
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
index 789f583e1d7..c0d7c84b69d 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
@@ -33,7 +33,7 @@ public struct EnumTest: Codable {
     public var enumNumber: EnumNumber?
     public var outerEnum: OuterEnum?
 
-    public init(enumString: EnumString?, enumStringRequired: EnumStringRequired, enumInteger: EnumInteger?, enumNumber: EnumNumber?, outerEnum: OuterEnum?) {
+    public init(enumString: EnumString? = nil, enumStringRequired: EnumStringRequired, enumInteger: EnumInteger? = nil, enumNumber: EnumNumber? = nil, outerEnum: OuterEnum? = nil) {
         self.enumString = enumString
         self.enumStringRequired = enumStringRequired
         self.enumInteger = enumInteger
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/File.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/File.swift
index abf3ccffc48..54ffb6e70e3 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/File.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/File.swift
@@ -13,7 +13,7 @@ public struct File: Codable {
     /** Test capitalization */
     public var sourceURI: String?
 
-    public init(sourceURI: String?) {
+    public init(sourceURI: String? = nil) {
         self.sourceURI = sourceURI
     }
 
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
index 532f1457939..3d70ffe0a59 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
@@ -12,7 +12,7 @@ public struct FileSchemaTestClass: Codable {
     public var file: File?
     public var files: [File]?
 
-    public init(file: File?, files: [File]?) {
+    public init(file: File? = nil, files: [File]? = nil) {
         self.file = file
         self.files = files
     }
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
index 20bd6d103b3..c934df71b34 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
@@ -23,7 +23,7 @@ public struct FormatTest: Codable {
     public var uuid: UUID?
     public var password: String
 
-    public init(integer: Int?, int32: Int?, int64: Int64?, number: Double, float: Float?, double: Double?, string: String?, byte: Data, binary: URL?, date: Date, dateTime: Date?, uuid: UUID?, password: String) {
+    public init(integer: Int? = nil, int32: Int? = nil, int64: Int64? = nil, number: Double, float: Float? = nil, double: Double? = nil, string: String? = nil, byte: Data, binary: URL? = nil, date: Date, dateTime: Date? = nil, uuid: UUID? = nil, password: String) {
         self.integer = integer
         self.int32 = int32
         self.int64 = int64
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
index 906ddb06fb1..a6d3567e885 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
@@ -12,7 +12,7 @@ public struct HasOnlyReadOnly: Codable {
     public var bar: String?
     public var foo: String?
 
-    public init(bar: String?, foo: String?) {
+    public init(bar: String? = nil, foo: String? = nil) {
         self.bar = bar
         self.foo = foo
     }
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/List.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/List.swift
index fe13d302ccb..6de49531ac1 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/List.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/List.swift
@@ -11,7 +11,7 @@ public struct List: Codable {
 
     public var _123list: String?
 
-    public init(_123list: String?) {
+    public init(_123list: String? = nil) {
         self._123list = _123list
     }
 
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
index 4b6037f378e..a9762da6155 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
@@ -18,7 +18,7 @@ public struct MapTest: Codable {
     public var directMap: [String: Bool]?
     public var indirectMap: StringBooleanMap?
 
-    public init(mapMapOfString: [String: [String: String]]?, mapOfEnumString: [String: String]?, directMap: [String: Bool]?, indirectMap: StringBooleanMap?) {
+    public init(mapMapOfString: [String: [String: String]]? = nil, mapOfEnumString: [String: String]? = nil, directMap: [String: Bool]? = nil, indirectMap: StringBooleanMap? = nil) {
         self.mapMapOfString = mapMapOfString
         self.mapOfEnumString = mapOfEnumString
         self.directMap = directMap
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
index c3deb2f2893..f1d081064b6 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
@@ -13,7 +13,7 @@ public struct MixedPropertiesAndAdditionalPropertiesClass: Codable {
     public var dateTime: Date?
     public var map: [String: Animal]?
 
-    public init(uuid: UUID?, dateTime: Date?, map: [String: Animal]?) {
+    public init(uuid: UUID? = nil, dateTime: Date? = nil, map: [String: Animal]? = nil) {
         self.uuid = uuid
         self.dateTime = dateTime
         self.map = map
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
index b61db7d6e71..6365e8799f7 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
@@ -13,7 +13,7 @@ public struct Model200Response: Codable {
     public var name: Int?
     public var _class: String?
 
-    public init(name: Int?, _class: String?) {
+    public init(name: Int? = nil, _class: String? = nil) {
         self.name = name
         self._class = _class
     }
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Name.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
index 8ab4db44b73..5797209dce3 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
@@ -15,7 +15,7 @@ public struct Name: Codable {
     public var property: String?
     public var _123number: Int?
 
-    public init(name: Int, snakeCase: Int?, property: String?, _123number: Int?) {
+    public init(name: Int, snakeCase: Int? = nil, property: String? = nil, _123number: Int? = nil) {
         self.name = name
         self.snakeCase = snakeCase
         self.property = property
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
index 4d1dafcc2c1..979335c098b 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
@@ -11,7 +11,7 @@ public struct NumberOnly: Codable {
 
     public var justNumber: Double?
 
-    public init(justNumber: Double?) {
+    public init(justNumber: Double? = nil) {
         self.justNumber = justNumber
     }
 
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Order.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
index 40c30cc8609..f1817f7792a 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
@@ -22,7 +22,7 @@ public struct Order: Codable {
     public var status: Status?
     public var complete: Bool? = false
 
-    public init(id: Int64?, petId: Int64?, quantity: Int?, shipDate: Date?, status: Status?, complete: Bool?) {
+    public init(id: Int64? = nil, petId: Int64? = nil, quantity: Int? = nil, shipDate: Date? = nil, status: Status? = nil, complete: Bool? = nil) {
         self.id = id
         self.petId = petId
         self.quantity = quantity
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
index 18c3a024f12..d01e8da2166 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
@@ -13,7 +13,7 @@ public struct OuterComposite: Codable {
     public var myString: String?
     public var myBoolean: Bool?
 
-    public init(myNumber: Double?, myString: String?, myBoolean: Bool?) {
+    public init(myNumber: Double? = nil, myString: String? = nil, myBoolean: Bool? = nil) {
         self.myNumber = myNumber
         self.myString = myString
         self.myBoolean = myBoolean
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
index b9ce0e93325..caea19425d8 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
@@ -22,7 +22,7 @@ public struct Pet: Codable {
     /** pet status in the store */
     public var status: Status?
 
-    public init(id: Int64?, category: Category?, name: String, photoUrls: [String], tags: [Tag]?, status: Status?) {
+    public init(id: Int64? = nil, category: Category? = nil, name: String, photoUrls: [String], tags: [Tag]? = nil, status: Status? = nil) {
         self.id = id
         self.category = category
         self.name = name
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
index 0acd21fd100..f643334038e 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
@@ -12,7 +12,7 @@ public struct ReadOnlyFirst: Codable {
     public var bar: String?
     public var baz: String?
 
-    public init(bar: String?, baz: String?) {
+    public init(bar: String? = nil, baz: String? = nil) {
         self.bar = bar
         self.baz = baz
     }
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Return.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
index c223f993a69..45479e2b0de 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
@@ -12,7 +12,7 @@ public struct Return: Codable {
 
     public var _return: Int?
 
-    public init(_return: Int?) {
+    public init(_return: Int? = nil) {
         self._return = _return
     }
 
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
index 6e8650f76d8..8515496eb27 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
@@ -11,7 +11,7 @@ public struct SpecialModelName: Codable {
 
     public var specialPropertyName: Int64?
 
-    public init(specialPropertyName: Int64?) {
+    public init(specialPropertyName: Int64? = nil) {
         self.specialPropertyName = specialPropertyName
     }
 
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
index 4dd8a9a9f5a..82c02f04b69 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
@@ -12,7 +12,7 @@ public struct Tag: Codable {
     public var id: Int64?
     public var name: String?
 
-    public init(id: Int64?, name: String?) {
+    public init(id: Int64? = nil, name: String? = nil) {
         self.id = id
         self.name = name
     }
diff --git a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/User.swift b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/User.swift
index 79f271ed735..03e2736bd23 100644
--- a/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/User.swift
+++ b/samples/client/petstore/swift5/promisekitLibrary/PetstoreClient/Classes/OpenAPIs/Models/User.swift
@@ -19,7 +19,7 @@ public struct User: Codable {
     /** User Status */
     public var userStatus: Int?
 
-    public init(id: Int64?, username: String?, firstName: String?, lastName: String?, email: String?, password: String?, phone: String?, userStatus: Int?) {
+    public init(id: Int64? = nil, username: String? = nil, firstName: String? = nil, lastName: String? = nil, email: String? = nil, password: String? = nil, phone: String? = nil, userStatus: Int? = nil) {
         self.id = id
         self.username = username
         self.firstName = firstName
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
index 3fda7052a7d..d7144747d6d 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
@@ -12,7 +12,7 @@ public struct AdditionalPropertiesClass: Codable {
     public private(set) var mapString: [String: String]?
     public private(set) var mapMapString: [String: [String: String]]?
 
-    public init(mapString: [String: String]?, mapMapString: [String: [String: String]]?) {
+    public init(mapString: [String: String]? = nil, mapMapString: [String: [String: String]]? = nil) {
         self.mapString = mapString
         self.mapMapString = mapMapString
     }
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
index af59c2a9ef6..7daa5138de0 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
@@ -12,7 +12,7 @@ public struct Animal: Codable {
     public private(set) var className: String
     public private(set) var color: String? = "red"
 
-    public init(className: String, color: String?) {
+    public init(className: String, color: String? = nil) {
         self.className = className
         self.color = color
     }
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
index a89768595cc..2046c61cab1 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
@@ -13,7 +13,7 @@ public struct ApiResponse: Codable {
     public private(set) var type: String?
     public private(set) var message: String?
 
-    public init(code: Int?, type: String?, message: String?) {
+    public init(code: Int? = nil, type: String? = nil, message: String? = nil) {
         self.code = code
         self.type = type
         self.message = message
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
index a2593b7c1a3..34d3808c996 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
@@ -11,7 +11,7 @@ public struct ArrayOfArrayOfNumberOnly: Codable {
 
     public private(set) var arrayArrayNumber: [[Double]]?
 
-    public init(arrayArrayNumber: [[Double]]?) {
+    public init(arrayArrayNumber: [[Double]]? = nil) {
         self.arrayArrayNumber = arrayArrayNumber
     }
 
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
index c5edf110053..05698f00cf3 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
@@ -11,7 +11,7 @@ public struct ArrayOfNumberOnly: Codable {
 
     public private(set) var arrayNumber: [Double]?
 
-    public init(arrayNumber: [Double]?) {
+    public init(arrayNumber: [Double]? = nil) {
         self.arrayNumber = arrayNumber
     }
 
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
index 8ad39b8c09f..1175bd6ea59 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
@@ -13,7 +13,7 @@ public struct ArrayTest: Codable {
     public private(set) var arrayArrayOfInteger: [[Int64]]?
     public private(set) var arrayArrayOfModel: [[ReadOnlyFirst]]?
 
-    public init(arrayOfString: [String]?, arrayArrayOfInteger: [[Int64]]?, arrayArrayOfModel: [[ReadOnlyFirst]]?) {
+    public init(arrayOfString: [String]? = nil, arrayArrayOfInteger: [[Int64]]? = nil, arrayArrayOfModel: [[ReadOnlyFirst]]? = nil) {
         self.arrayOfString = arrayOfString
         self.arrayArrayOfInteger = arrayArrayOfInteger
         self.arrayArrayOfModel = arrayArrayOfModel
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
index eb3d6777e52..ad1a6d34ede 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
@@ -17,7 +17,7 @@ public struct Capitalization: Codable {
     /** Name of the pet  */
     public private(set) var ATT_NAME: String?
 
-    public init(smallCamel: String?, capitalCamel: String?, smallSnake: String?, capitalSnake: String?, sCAETHFlowPoints: String?, ATT_NAME: String?) {
+    public init(smallCamel: String? = nil, capitalCamel: String? = nil, smallSnake: String? = nil, capitalSnake: String? = nil, sCAETHFlowPoints: String? = nil, ATT_NAME: String? = nil) {
         self.smallCamel = smallCamel
         self.capitalCamel = capitalCamel
         self.smallSnake = smallSnake
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
index 2978b016f98..44de9d88fe3 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
@@ -13,7 +13,7 @@ public struct Cat: Codable {
     public private(set) var color: String? = "red"
     public private(set) var declawed: Bool?
 
-    public init(className: String, color: String?, declawed: Bool?) {
+    public init(className: String, color: String? = nil, declawed: Bool? = nil) {
         self.className = className
         self.color = color
         self.declawed = declawed
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
index 4ab80fbcd99..7cfc1de3a15 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
@@ -11,7 +11,7 @@ public struct CatAllOf: Codable {
 
     public private(set) var declawed: Bool?
 
-    public init(declawed: Bool?) {
+    public init(declawed: Bool? = nil) {
         self.declawed = declawed
     }
 
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Category.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
index 3482703a6b4..5b2ec18905f 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
@@ -12,7 +12,7 @@ public struct Category: Codable {
     public private(set) var id: Int64?
     public private(set) var name: String = "default-name"
 
-    public init(id: Int64?, name: String) {
+    public init(id: Int64? = nil, name: String) {
         self.id = id
         self.name = name
     }
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
index 319d88a70f7..75ab2a99cbb 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
@@ -12,7 +12,7 @@ public struct ClassModel: Codable {
 
     public private(set) var _class: String?
 
-    public init(_class: String?) {
+    public init(_class: String? = nil) {
         self._class = _class
     }
 
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Client.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
index 5dd8cc3062d..6e416e1d15e 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
@@ -11,7 +11,7 @@ public struct Client: Codable {
 
     public private(set) var client: String?
 
-    public init(client: String?) {
+    public init(client: String? = nil) {
         self.client = client
     }
 
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
index 16ab196b872..1e660e05bd2 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
@@ -13,7 +13,7 @@ public struct Dog: Codable {
     public private(set) var color: String? = "red"
     public private(set) var breed: String?
 
-    public init(className: String, color: String?, breed: String?) {
+    public init(className: String, color: String? = nil, breed: String? = nil) {
         self.className = className
         self.color = color
         self.breed = breed
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
index d8a838725cb..b0e9fa0c842 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
@@ -11,7 +11,7 @@ public struct DogAllOf: Codable {
 
     public private(set) var breed: String?
 
-    public init(breed: String?) {
+    public init(breed: String? = nil) {
         self.breed = breed
     }
 
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
index d9ce69e9fc8..aaba025176a 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
@@ -20,7 +20,7 @@ public struct EnumArrays: Codable {
     public private(set) var justSymbol: JustSymbol?
     public private(set) var arrayEnum: [ArrayEnum]?
 
-    public init(justSymbol: JustSymbol?, arrayEnum: [ArrayEnum]?) {
+    public init(justSymbol: JustSymbol? = nil, arrayEnum: [ArrayEnum]? = nil) {
         self.justSymbol = justSymbol
         self.arrayEnum = arrayEnum
     }
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
index 2b114d422d1..0fb1c191009 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
@@ -33,7 +33,7 @@ public struct EnumTest: Codable {
     public private(set) var enumNumber: EnumNumber?
     public private(set) var outerEnum: OuterEnum?
 
-    public init(enumString: EnumString?, enumStringRequired: EnumStringRequired, enumInteger: EnumInteger?, enumNumber: EnumNumber?, outerEnum: OuterEnum?) {
+    public init(enumString: EnumString? = nil, enumStringRequired: EnumStringRequired, enumInteger: EnumInteger? = nil, enumNumber: EnumNumber? = nil, outerEnum: OuterEnum? = nil) {
         self.enumString = enumString
         self.enumStringRequired = enumStringRequired
         self.enumInteger = enumInteger
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/File.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/File.swift
index eeab5819441..89b0f40d736 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/File.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/File.swift
@@ -13,7 +13,7 @@ public struct File: Codable {
     /** Test capitalization */
     public private(set) var sourceURI: String?
 
-    public init(sourceURI: String?) {
+    public init(sourceURI: String? = nil) {
         self.sourceURI = sourceURI
     }
 
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
index 94574ca9955..6e914ed4db4 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
@@ -12,7 +12,7 @@ public struct FileSchemaTestClass: Codable {
     public private(set) var file: File?
     public private(set) var files: [File]?
 
-    public init(file: File?, files: [File]?) {
+    public init(file: File? = nil, files: [File]? = nil) {
         self.file = file
         self.files = files
     }
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
index 57bbd464b51..571dd3c36fe 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
@@ -23,7 +23,7 @@ public struct FormatTest: Codable {
     public private(set) var uuid: UUID?
     public private(set) var password: String
 
-    public init(integer: Int?, int32: Int?, int64: Int64?, number: Double, float: Float?, double: Double?, string: String?, byte: Data, binary: URL?, date: Date, dateTime: Date?, uuid: UUID?, password: String) {
+    public init(integer: Int? = nil, int32: Int? = nil, int64: Int64? = nil, number: Double, float: Float? = nil, double: Double? = nil, string: String? = nil, byte: Data, binary: URL? = nil, date: Date, dateTime: Date? = nil, uuid: UUID? = nil, password: String) {
         self.integer = integer
         self.int32 = int32
         self.int64 = int64
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
index 4de261f092d..223a6433fdc 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
@@ -12,7 +12,7 @@ public struct HasOnlyReadOnly: Codable {
     public private(set) var bar: String?
     public private(set) var foo: String?
 
-    public init(bar: String?, foo: String?) {
+    public init(bar: String? = nil, foo: String? = nil) {
         self.bar = bar
         self.foo = foo
     }
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/List.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/List.swift
index 135160ff8de..f1d47b6e07e 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/List.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/List.swift
@@ -11,7 +11,7 @@ public struct List: Codable {
 
     public private(set) var _123list: String?
 
-    public init(_123list: String?) {
+    public init(_123list: String? = nil) {
         self._123list = _123list
     }
 
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
index ebd9dd5b5bc..e0d9e0bc2d5 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
@@ -18,7 +18,7 @@ public struct MapTest: Codable {
     public private(set) var directMap: [String: Bool]?
     public private(set) var indirectMap: StringBooleanMap?
 
-    public init(mapMapOfString: [String: [String: String]]?, mapOfEnumString: [String: String]?, directMap: [String: Bool]?, indirectMap: StringBooleanMap?) {
+    public init(mapMapOfString: [String: [String: String]]? = nil, mapOfEnumString: [String: String]? = nil, directMap: [String: Bool]? = nil, indirectMap: StringBooleanMap? = nil) {
         self.mapMapOfString = mapMapOfString
         self.mapOfEnumString = mapOfEnumString
         self.directMap = directMap
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
index dc1ee0461be..6e0b65a7092 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
@@ -13,7 +13,7 @@ public struct MixedPropertiesAndAdditionalPropertiesClass: Codable {
     public private(set) var dateTime: Date?
     public private(set) var map: [String: Animal]?
 
-    public init(uuid: UUID?, dateTime: Date?, map: [String: Animal]?) {
+    public init(uuid: UUID? = nil, dateTime: Date? = nil, map: [String: Animal]? = nil) {
         self.uuid = uuid
         self.dateTime = dateTime
         self.map = map
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
index a0f7127ef65..b6591caa950 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
@@ -13,7 +13,7 @@ public struct Model200Response: Codable {
     public private(set) var name: Int?
     public private(set) var _class: String?
 
-    public init(name: Int?, _class: String?) {
+    public init(name: Int? = nil, _class: String? = nil) {
         self.name = name
         self._class = _class
     }
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Name.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
index ee70b1f6ee9..69e07f057ed 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
@@ -15,7 +15,7 @@ public struct Name: Codable {
     public private(set) var property: String?
     public private(set) var _123number: Int?
 
-    public init(name: Int, snakeCase: Int?, property: String?, _123number: Int?) {
+    public init(name: Int, snakeCase: Int? = nil, property: String? = nil, _123number: Int? = nil) {
         self.name = name
         self.snakeCase = snakeCase
         self.property = property
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
index 007dfab800c..77fdfc7a1cd 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
@@ -11,7 +11,7 @@ public struct NumberOnly: Codable {
 
     public private(set) var justNumber: Double?
 
-    public init(justNumber: Double?) {
+    public init(justNumber: Double? = nil) {
         self.justNumber = justNumber
     }
 
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Order.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
index 41a1d7d664e..966cc61ac87 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
@@ -22,7 +22,7 @@ public struct Order: Codable {
     public private(set) var status: Status?
     public private(set) var complete: Bool? = false
 
-    public init(id: Int64?, petId: Int64?, quantity: Int?, shipDate: Date?, status: Status?, complete: Bool?) {
+    public init(id: Int64? = nil, petId: Int64? = nil, quantity: Int? = nil, shipDate: Date? = nil, status: Status? = nil, complete: Bool? = nil) {
         self.id = id
         self.petId = petId
         self.quantity = quantity
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
index df6d2512d6e..721ec8e983d 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
@@ -13,7 +13,7 @@ public struct OuterComposite: Codable {
     public private(set) var myString: String?
     public private(set) var myBoolean: Bool?
 
-    public init(myNumber: Double?, myString: String?, myBoolean: Bool?) {
+    public init(myNumber: Double? = nil, myString: String? = nil, myBoolean: Bool? = nil) {
         self.myNumber = myNumber
         self.myString = myString
         self.myBoolean = myBoolean
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
index 7b99ef33751..f13bd2f2c31 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
@@ -22,7 +22,7 @@ public struct Pet: Codable {
     /** pet status in the store */
     public private(set) var status: Status?
 
-    public init(id: Int64?, category: Category?, name: String, photoUrls: [String], tags: [Tag]?, status: Status?) {
+    public init(id: Int64? = nil, category: Category? = nil, name: String, photoUrls: [String], tags: [Tag]? = nil, status: Status? = nil) {
         self.id = id
         self.category = category
         self.name = name
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
index 30cd4837cc7..914adf7f7ae 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
@@ -12,7 +12,7 @@ public struct ReadOnlyFirst: Codable {
     public private(set) var bar: String?
     public private(set) var baz: String?
 
-    public init(bar: String?, baz: String?) {
+    public init(bar: String? = nil, baz: String? = nil) {
         self.bar = bar
         self.baz = baz
     }
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Return.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
index b28b6e99d77..470353cdce9 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
@@ -12,7 +12,7 @@ public struct Return: Codable {
 
     public private(set) var _return: Int?
 
-    public init(_return: Int?) {
+    public init(_return: Int? = nil) {
         self._return = _return
     }
 
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
index 266833a0dbc..ad0619f0471 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
@@ -11,7 +11,7 @@ public struct SpecialModelName: Codable {
 
     public private(set) var specialPropertyName: Int64?
 
-    public init(specialPropertyName: Int64?) {
+    public init(specialPropertyName: Int64? = nil) {
         self.specialPropertyName = specialPropertyName
     }
 
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
index f827ccf107a..08c29fb3f36 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
@@ -12,7 +12,7 @@ public struct Tag: Codable {
     public private(set) var id: Int64?
     public private(set) var name: String?
 
-    public init(id: Int64?, name: String?) {
+    public init(id: Int64? = nil, name: String? = nil) {
         self.id = id
         self.name = name
     }
diff --git a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/User.swift b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/User.swift
index 9fba7de8182..3826f33ed6a 100644
--- a/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/User.swift
+++ b/samples/client/petstore/swift5/readonlyProperties/PetstoreClient/Classes/OpenAPIs/Models/User.swift
@@ -19,7 +19,7 @@ public struct User: Codable {
     /** User Status */
     public private(set) var userStatus: Int?
 
-    public init(id: Int64?, username: String?, firstName: String?, lastName: String?, email: String?, password: String?, phone: String?, userStatus: Int?) {
+    public init(id: Int64? = nil, username: String? = nil, firstName: String? = nil, lastName: String? = nil, email: String? = nil, password: String? = nil, phone: String? = nil, userStatus: Int? = nil) {
         self.id = id
         self.username = username
         self.firstName = firstName
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
index 1af03153596..81020425ad1 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
@@ -12,7 +12,7 @@ public struct AdditionalPropertiesClass: Codable {
     public var mapString: [String: String]?
     public var mapMapString: [String: [String: String]]?
 
-    public init(mapString: [String: String]?, mapMapString: [String: [String: String]]?) {
+    public init(mapString: [String: String]? = nil, mapMapString: [String: [String: String]]? = nil) {
         self.mapString = mapString
         self.mapMapString = mapMapString
     }
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
index 5ed9f31e2a3..c34ac85ac63 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
@@ -12,7 +12,7 @@ public struct Animal: Codable {
     public var className: String
     public var color: String? = "red"
 
-    public init(className: String, color: String?) {
+    public init(className: String, color: String? = nil) {
         self.className = className
         self.color = color
     }
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
index ec270da8907..6ad3d808a97 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
@@ -13,7 +13,7 @@ public struct ApiResponse: Codable {
     public var type: String?
     public var message: String?
 
-    public init(code: Int?, type: String?, message: String?) {
+    public init(code: Int? = nil, type: String? = nil, message: String? = nil) {
         self.code = code
         self.type = type
         self.message = message
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
index 6c252ed475b..6d99f90fdd1 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
@@ -11,7 +11,7 @@ public struct ArrayOfArrayOfNumberOnly: Codable {
 
     public var arrayArrayNumber: [[Double]]?
 
-    public init(arrayArrayNumber: [[Double]]?) {
+    public init(arrayArrayNumber: [[Double]]? = nil) {
         self.arrayArrayNumber = arrayArrayNumber
     }
 
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
index e84eb5d6502..d59c529ef65 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
@@ -11,7 +11,7 @@ public struct ArrayOfNumberOnly: Codable {
 
     public var arrayNumber: [Double]?
 
-    public init(arrayNumber: [Double]?) {
+    public init(arrayNumber: [Double]? = nil) {
         self.arrayNumber = arrayNumber
     }
 
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
index d2140933d18..fdab67b0c59 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
@@ -13,7 +13,7 @@ public struct ArrayTest: Codable {
     public var arrayArrayOfInteger: [[Int64]]?
     public var arrayArrayOfModel: [[ReadOnlyFirst]]?
 
-    public init(arrayOfString: [String]?, arrayArrayOfInteger: [[Int64]]?, arrayArrayOfModel: [[ReadOnlyFirst]]?) {
+    public init(arrayOfString: [String]? = nil, arrayArrayOfInteger: [[Int64]]? = nil, arrayArrayOfModel: [[ReadOnlyFirst]]? = nil) {
         self.arrayOfString = arrayOfString
         self.arrayArrayOfInteger = arrayArrayOfInteger
         self.arrayArrayOfModel = arrayArrayOfModel
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
index d1b3b27616e..a7f8abe9719 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
@@ -17,7 +17,7 @@ public struct Capitalization: Codable {
     /** Name of the pet  */
     public var ATT_NAME: String?
 
-    public init(smallCamel: String?, capitalCamel: String?, smallSnake: String?, capitalSnake: String?, sCAETHFlowPoints: String?, ATT_NAME: String?) {
+    public init(smallCamel: String? = nil, capitalCamel: String? = nil, smallSnake: String? = nil, capitalSnake: String? = nil, sCAETHFlowPoints: String? = nil, ATT_NAME: String? = nil) {
         self.smallCamel = smallCamel
         self.capitalCamel = capitalCamel
         self.smallSnake = smallSnake
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
index 7ab887f3113..884020d1a72 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
@@ -13,7 +13,7 @@ public struct Cat: Codable {
     public var color: String? = "red"
     public var declawed: Bool?
 
-    public init(className: String, color: String?, declawed: Bool?) {
+    public init(className: String, color: String? = nil, declawed: Bool? = nil) {
         self.className = className
         self.color = color
         self.declawed = declawed
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
index a51ad0dffab..c7178efcb16 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
@@ -11,7 +11,7 @@ public struct CatAllOf: Codable {
 
     public var declawed: Bool?
 
-    public init(declawed: Bool?) {
+    public init(declawed: Bool? = nil) {
         self.declawed = declawed
     }
 
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Category.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
index eb8f7e5e197..78bf6826d69 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
@@ -12,7 +12,7 @@ public struct Category: Codable {
     public var id: Int64?
     public var name: String = "default-name"
 
-    public init(id: Int64?, name: String) {
+    public init(id: Int64? = nil, name: String) {
         self.id = id
         self.name = name
     }
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
index e2a7d4427a0..d7299a05856 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
@@ -12,7 +12,7 @@ public struct ClassModel: Codable {
 
     public var _class: String?
 
-    public init(_class: String?) {
+    public init(_class: String? = nil) {
         self._class = _class
     }
 
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Client.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
index 00245ca3728..c8e0b51314d 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
@@ -11,7 +11,7 @@ public struct Client: Codable {
 
     public var client: String?
 
-    public init(client: String?) {
+    public init(client: String? = nil) {
         self.client = client
     }
 
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
index 492c1228008..e7e0efa931e 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
@@ -13,7 +13,7 @@ public struct Dog: Codable {
     public var color: String? = "red"
     public var breed: String?
 
-    public init(className: String, color: String?, breed: String?) {
+    public init(className: String, color: String? = nil, breed: String? = nil) {
         self.className = className
         self.color = color
         self.breed = breed
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
index 7786f8acc5a..1f61ed3c343 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
@@ -11,7 +11,7 @@ public struct DogAllOf: Codable {
 
     public var breed: String?
 
-    public init(breed: String?) {
+    public init(breed: String? = nil) {
         self.breed = breed
     }
 
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
index 9844e7c40e3..10536376ccc 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
@@ -20,7 +20,7 @@ public struct EnumArrays: Codable {
     public var justSymbol: JustSymbol?
     public var arrayEnum: [ArrayEnum]?
 
-    public init(justSymbol: JustSymbol?, arrayEnum: [ArrayEnum]?) {
+    public init(justSymbol: JustSymbol? = nil, arrayEnum: [ArrayEnum]? = nil) {
         self.justSymbol = justSymbol
         self.arrayEnum = arrayEnum
     }
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
index 789f583e1d7..c0d7c84b69d 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
@@ -33,7 +33,7 @@ public struct EnumTest: Codable {
     public var enumNumber: EnumNumber?
     public var outerEnum: OuterEnum?
 
-    public init(enumString: EnumString?, enumStringRequired: EnumStringRequired, enumInteger: EnumInteger?, enumNumber: EnumNumber?, outerEnum: OuterEnum?) {
+    public init(enumString: EnumString? = nil, enumStringRequired: EnumStringRequired, enumInteger: EnumInteger? = nil, enumNumber: EnumNumber? = nil, outerEnum: OuterEnum? = nil) {
         self.enumString = enumString
         self.enumStringRequired = enumStringRequired
         self.enumInteger = enumInteger
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/File.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/File.swift
index abf3ccffc48..54ffb6e70e3 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/File.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/File.swift
@@ -13,7 +13,7 @@ public struct File: Codable {
     /** Test capitalization */
     public var sourceURI: String?
 
-    public init(sourceURI: String?) {
+    public init(sourceURI: String? = nil) {
         self.sourceURI = sourceURI
     }
 
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
index 532f1457939..3d70ffe0a59 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
@@ -12,7 +12,7 @@ public struct FileSchemaTestClass: Codable {
     public var file: File?
     public var files: [File]?
 
-    public init(file: File?, files: [File]?) {
+    public init(file: File? = nil, files: [File]? = nil) {
         self.file = file
         self.files = files
     }
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
index 20bd6d103b3..c934df71b34 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
@@ -23,7 +23,7 @@ public struct FormatTest: Codable {
     public var uuid: UUID?
     public var password: String
 
-    public init(integer: Int?, int32: Int?, int64: Int64?, number: Double, float: Float?, double: Double?, string: String?, byte: Data, binary: URL?, date: Date, dateTime: Date?, uuid: UUID?, password: String) {
+    public init(integer: Int? = nil, int32: Int? = nil, int64: Int64? = nil, number: Double, float: Float? = nil, double: Double? = nil, string: String? = nil, byte: Data, binary: URL? = nil, date: Date, dateTime: Date? = nil, uuid: UUID? = nil, password: String) {
         self.integer = integer
         self.int32 = int32
         self.int64 = int64
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
index 906ddb06fb1..a6d3567e885 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
@@ -12,7 +12,7 @@ public struct HasOnlyReadOnly: Codable {
     public var bar: String?
     public var foo: String?
 
-    public init(bar: String?, foo: String?) {
+    public init(bar: String? = nil, foo: String? = nil) {
         self.bar = bar
         self.foo = foo
     }
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/List.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/List.swift
index fe13d302ccb..6de49531ac1 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/List.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/List.swift
@@ -11,7 +11,7 @@ public struct List: Codable {
 
     public var _123list: String?
 
-    public init(_123list: String?) {
+    public init(_123list: String? = nil) {
         self._123list = _123list
     }
 
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
index 4b6037f378e..a9762da6155 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
@@ -18,7 +18,7 @@ public struct MapTest: Codable {
     public var directMap: [String: Bool]?
     public var indirectMap: StringBooleanMap?
 
-    public init(mapMapOfString: [String: [String: String]]?, mapOfEnumString: [String: String]?, directMap: [String: Bool]?, indirectMap: StringBooleanMap?) {
+    public init(mapMapOfString: [String: [String: String]]? = nil, mapOfEnumString: [String: String]? = nil, directMap: [String: Bool]? = nil, indirectMap: StringBooleanMap? = nil) {
         self.mapMapOfString = mapMapOfString
         self.mapOfEnumString = mapOfEnumString
         self.directMap = directMap
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
index c3deb2f2893..f1d081064b6 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
@@ -13,7 +13,7 @@ public struct MixedPropertiesAndAdditionalPropertiesClass: Codable {
     public var dateTime: Date?
     public var map: [String: Animal]?
 
-    public init(uuid: UUID?, dateTime: Date?, map: [String: Animal]?) {
+    public init(uuid: UUID? = nil, dateTime: Date? = nil, map: [String: Animal]? = nil) {
         self.uuid = uuid
         self.dateTime = dateTime
         self.map = map
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
index b61db7d6e71..6365e8799f7 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
@@ -13,7 +13,7 @@ public struct Model200Response: Codable {
     public var name: Int?
     public var _class: String?
 
-    public init(name: Int?, _class: String?) {
+    public init(name: Int? = nil, _class: String? = nil) {
         self.name = name
         self._class = _class
     }
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Name.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
index 8ab4db44b73..5797209dce3 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
@@ -15,7 +15,7 @@ public struct Name: Codable {
     public var property: String?
     public var _123number: Int?
 
-    public init(name: Int, snakeCase: Int?, property: String?, _123number: Int?) {
+    public init(name: Int, snakeCase: Int? = nil, property: String? = nil, _123number: Int? = nil) {
         self.name = name
         self.snakeCase = snakeCase
         self.property = property
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
index 4d1dafcc2c1..979335c098b 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
@@ -11,7 +11,7 @@ public struct NumberOnly: Codable {
 
     public var justNumber: Double?
 
-    public init(justNumber: Double?) {
+    public init(justNumber: Double? = nil) {
         self.justNumber = justNumber
     }
 
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Order.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
index 40c30cc8609..f1817f7792a 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
@@ -22,7 +22,7 @@ public struct Order: Codable {
     public var status: Status?
     public var complete: Bool? = false
 
-    public init(id: Int64?, petId: Int64?, quantity: Int?, shipDate: Date?, status: Status?, complete: Bool?) {
+    public init(id: Int64? = nil, petId: Int64? = nil, quantity: Int? = nil, shipDate: Date? = nil, status: Status? = nil, complete: Bool? = nil) {
         self.id = id
         self.petId = petId
         self.quantity = quantity
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
index 18c3a024f12..d01e8da2166 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
@@ -13,7 +13,7 @@ public struct OuterComposite: Codable {
     public var myString: String?
     public var myBoolean: Bool?
 
-    public init(myNumber: Double?, myString: String?, myBoolean: Bool?) {
+    public init(myNumber: Double? = nil, myString: String? = nil, myBoolean: Bool? = nil) {
         self.myNumber = myNumber
         self.myString = myString
         self.myBoolean = myBoolean
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
index b9ce0e93325..caea19425d8 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
@@ -22,7 +22,7 @@ public struct Pet: Codable {
     /** pet status in the store */
     public var status: Status?
 
-    public init(id: Int64?, category: Category?, name: String, photoUrls: [String], tags: [Tag]?, status: Status?) {
+    public init(id: Int64? = nil, category: Category? = nil, name: String, photoUrls: [String], tags: [Tag]? = nil, status: Status? = nil) {
         self.id = id
         self.category = category
         self.name = name
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
index 0acd21fd100..f643334038e 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
@@ -12,7 +12,7 @@ public struct ReadOnlyFirst: Codable {
     public var bar: String?
     public var baz: String?
 
-    public init(bar: String?, baz: String?) {
+    public init(bar: String? = nil, baz: String? = nil) {
         self.bar = bar
         self.baz = baz
     }
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Return.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
index c223f993a69..45479e2b0de 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
@@ -12,7 +12,7 @@ public struct Return: Codable {
 
     public var _return: Int?
 
-    public init(_return: Int?) {
+    public init(_return: Int? = nil) {
         self._return = _return
     }
 
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
index 6e8650f76d8..8515496eb27 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
@@ -11,7 +11,7 @@ public struct SpecialModelName: Codable {
 
     public var specialPropertyName: Int64?
 
-    public init(specialPropertyName: Int64?) {
+    public init(specialPropertyName: Int64? = nil) {
         self.specialPropertyName = specialPropertyName
     }
 
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
index 4dd8a9a9f5a..82c02f04b69 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
@@ -12,7 +12,7 @@ public struct Tag: Codable {
     public var id: Int64?
     public var name: String?
 
-    public init(id: Int64?, name: String?) {
+    public init(id: Int64? = nil, name: String? = nil) {
         self.id = id
         self.name = name
     }
diff --git a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/User.swift b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/User.swift
index 79f271ed735..03e2736bd23 100644
--- a/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/User.swift
+++ b/samples/client/petstore/swift5/resultLibrary/PetstoreClient/Classes/OpenAPIs/Models/User.swift
@@ -19,7 +19,7 @@ public struct User: Codable {
     /** User Status */
     public var userStatus: Int?
 
-    public init(id: Int64?, username: String?, firstName: String?, lastName: String?, email: String?, password: String?, phone: String?, userStatus: Int?) {
+    public init(id: Int64? = nil, username: String? = nil, firstName: String? = nil, lastName: String? = nil, email: String? = nil, password: String? = nil, phone: String? = nil, userStatus: Int? = nil) {
         self.id = id
         self.username = username
         self.firstName = firstName
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
index 1af03153596..81020425ad1 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
@@ -12,7 +12,7 @@ public struct AdditionalPropertiesClass: Codable {
     public var mapString: [String: String]?
     public var mapMapString: [String: [String: String]]?
 
-    public init(mapString: [String: String]?, mapMapString: [String: [String: String]]?) {
+    public init(mapString: [String: String]? = nil, mapMapString: [String: [String: String]]? = nil) {
         self.mapString = mapString
         self.mapMapString = mapMapString
     }
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
index 5ed9f31e2a3..c34ac85ac63 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
@@ -12,7 +12,7 @@ public struct Animal: Codable {
     public var className: String
     public var color: String? = "red"
 
-    public init(className: String, color: String?) {
+    public init(className: String, color: String? = nil) {
         self.className = className
         self.color = color
     }
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
index ec270da8907..6ad3d808a97 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
@@ -13,7 +13,7 @@ public struct ApiResponse: Codable {
     public var type: String?
     public var message: String?
 
-    public init(code: Int?, type: String?, message: String?) {
+    public init(code: Int? = nil, type: String? = nil, message: String? = nil) {
         self.code = code
         self.type = type
         self.message = message
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
index 6c252ed475b..6d99f90fdd1 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
@@ -11,7 +11,7 @@ public struct ArrayOfArrayOfNumberOnly: Codable {
 
     public var arrayArrayNumber: [[Double]]?
 
-    public init(arrayArrayNumber: [[Double]]?) {
+    public init(arrayArrayNumber: [[Double]]? = nil) {
         self.arrayArrayNumber = arrayArrayNumber
     }
 
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
index e84eb5d6502..d59c529ef65 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
@@ -11,7 +11,7 @@ public struct ArrayOfNumberOnly: Codable {
 
     public var arrayNumber: [Double]?
 
-    public init(arrayNumber: [Double]?) {
+    public init(arrayNumber: [Double]? = nil) {
         self.arrayNumber = arrayNumber
     }
 
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
index d2140933d18..fdab67b0c59 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
@@ -13,7 +13,7 @@ public struct ArrayTest: Codable {
     public var arrayArrayOfInteger: [[Int64]]?
     public var arrayArrayOfModel: [[ReadOnlyFirst]]?
 
-    public init(arrayOfString: [String]?, arrayArrayOfInteger: [[Int64]]?, arrayArrayOfModel: [[ReadOnlyFirst]]?) {
+    public init(arrayOfString: [String]? = nil, arrayArrayOfInteger: [[Int64]]? = nil, arrayArrayOfModel: [[ReadOnlyFirst]]? = nil) {
         self.arrayOfString = arrayOfString
         self.arrayArrayOfInteger = arrayArrayOfInteger
         self.arrayArrayOfModel = arrayArrayOfModel
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
index d1b3b27616e..a7f8abe9719 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
@@ -17,7 +17,7 @@ public struct Capitalization: Codable {
     /** Name of the pet  */
     public var ATT_NAME: String?
 
-    public init(smallCamel: String?, capitalCamel: String?, smallSnake: String?, capitalSnake: String?, sCAETHFlowPoints: String?, ATT_NAME: String?) {
+    public init(smallCamel: String? = nil, capitalCamel: String? = nil, smallSnake: String? = nil, capitalSnake: String? = nil, sCAETHFlowPoints: String? = nil, ATT_NAME: String? = nil) {
         self.smallCamel = smallCamel
         self.capitalCamel = capitalCamel
         self.smallSnake = smallSnake
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
index 7ab887f3113..884020d1a72 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
@@ -13,7 +13,7 @@ public struct Cat: Codable {
     public var color: String? = "red"
     public var declawed: Bool?
 
-    public init(className: String, color: String?, declawed: Bool?) {
+    public init(className: String, color: String? = nil, declawed: Bool? = nil) {
         self.className = className
         self.color = color
         self.declawed = declawed
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
index a51ad0dffab..c7178efcb16 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
@@ -11,7 +11,7 @@ public struct CatAllOf: Codable {
 
     public var declawed: Bool?
 
-    public init(declawed: Bool?) {
+    public init(declawed: Bool? = nil) {
         self.declawed = declawed
     }
 
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Category.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
index eb8f7e5e197..78bf6826d69 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
@@ -12,7 +12,7 @@ public struct Category: Codable {
     public var id: Int64?
     public var name: String = "default-name"
 
-    public init(id: Int64?, name: String) {
+    public init(id: Int64? = nil, name: String) {
         self.id = id
         self.name = name
     }
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
index e2a7d4427a0..d7299a05856 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
@@ -12,7 +12,7 @@ public struct ClassModel: Codable {
 
     public var _class: String?
 
-    public init(_class: String?) {
+    public init(_class: String? = nil) {
         self._class = _class
     }
 
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Client.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
index 00245ca3728..c8e0b51314d 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
@@ -11,7 +11,7 @@ public struct Client: Codable {
 
     public var client: String?
 
-    public init(client: String?) {
+    public init(client: String? = nil) {
         self.client = client
     }
 
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
index 492c1228008..e7e0efa931e 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
@@ -13,7 +13,7 @@ public struct Dog: Codable {
     public var color: String? = "red"
     public var breed: String?
 
-    public init(className: String, color: String?, breed: String?) {
+    public init(className: String, color: String? = nil, breed: String? = nil) {
         self.className = className
         self.color = color
         self.breed = breed
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
index 7786f8acc5a..1f61ed3c343 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
@@ -11,7 +11,7 @@ public struct DogAllOf: Codable {
 
     public var breed: String?
 
-    public init(breed: String?) {
+    public init(breed: String? = nil) {
         self.breed = breed
     }
 
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
index 9844e7c40e3..10536376ccc 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
@@ -20,7 +20,7 @@ public struct EnumArrays: Codable {
     public var justSymbol: JustSymbol?
     public var arrayEnum: [ArrayEnum]?
 
-    public init(justSymbol: JustSymbol?, arrayEnum: [ArrayEnum]?) {
+    public init(justSymbol: JustSymbol? = nil, arrayEnum: [ArrayEnum]? = nil) {
         self.justSymbol = justSymbol
         self.arrayEnum = arrayEnum
     }
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
index 789f583e1d7..c0d7c84b69d 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
@@ -33,7 +33,7 @@ public struct EnumTest: Codable {
     public var enumNumber: EnumNumber?
     public var outerEnum: OuterEnum?
 
-    public init(enumString: EnumString?, enumStringRequired: EnumStringRequired, enumInteger: EnumInteger?, enumNumber: EnumNumber?, outerEnum: OuterEnum?) {
+    public init(enumString: EnumString? = nil, enumStringRequired: EnumStringRequired, enumInteger: EnumInteger? = nil, enumNumber: EnumNumber? = nil, outerEnum: OuterEnum? = nil) {
         self.enumString = enumString
         self.enumStringRequired = enumStringRequired
         self.enumInteger = enumInteger
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/File.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/File.swift
index abf3ccffc48..54ffb6e70e3 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/File.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/File.swift
@@ -13,7 +13,7 @@ public struct File: Codable {
     /** Test capitalization */
     public var sourceURI: String?
 
-    public init(sourceURI: String?) {
+    public init(sourceURI: String? = nil) {
         self.sourceURI = sourceURI
     }
 
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
index 532f1457939..3d70ffe0a59 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
@@ -12,7 +12,7 @@ public struct FileSchemaTestClass: Codable {
     public var file: File?
     public var files: [File]?
 
-    public init(file: File?, files: [File]?) {
+    public init(file: File? = nil, files: [File]? = nil) {
         self.file = file
         self.files = files
     }
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
index 20bd6d103b3..c934df71b34 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
@@ -23,7 +23,7 @@ public struct FormatTest: Codable {
     public var uuid: UUID?
     public var password: String
 
-    public init(integer: Int?, int32: Int?, int64: Int64?, number: Double, float: Float?, double: Double?, string: String?, byte: Data, binary: URL?, date: Date, dateTime: Date?, uuid: UUID?, password: String) {
+    public init(integer: Int? = nil, int32: Int? = nil, int64: Int64? = nil, number: Double, float: Float? = nil, double: Double? = nil, string: String? = nil, byte: Data, binary: URL? = nil, date: Date, dateTime: Date? = nil, uuid: UUID? = nil, password: String) {
         self.integer = integer
         self.int32 = int32
         self.int64 = int64
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
index 906ddb06fb1..a6d3567e885 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
@@ -12,7 +12,7 @@ public struct HasOnlyReadOnly: Codable {
     public var bar: String?
     public var foo: String?
 
-    public init(bar: String?, foo: String?) {
+    public init(bar: String? = nil, foo: String? = nil) {
         self.bar = bar
         self.foo = foo
     }
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/List.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/List.swift
index fe13d302ccb..6de49531ac1 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/List.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/List.swift
@@ -11,7 +11,7 @@ public struct List: Codable {
 
     public var _123list: String?
 
-    public init(_123list: String?) {
+    public init(_123list: String? = nil) {
         self._123list = _123list
     }
 
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
index 4b6037f378e..a9762da6155 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
@@ -18,7 +18,7 @@ public struct MapTest: Codable {
     public var directMap: [String: Bool]?
     public var indirectMap: StringBooleanMap?
 
-    public init(mapMapOfString: [String: [String: String]]?, mapOfEnumString: [String: String]?, directMap: [String: Bool]?, indirectMap: StringBooleanMap?) {
+    public init(mapMapOfString: [String: [String: String]]? = nil, mapOfEnumString: [String: String]? = nil, directMap: [String: Bool]? = nil, indirectMap: StringBooleanMap? = nil) {
         self.mapMapOfString = mapMapOfString
         self.mapOfEnumString = mapOfEnumString
         self.directMap = directMap
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
index c3deb2f2893..f1d081064b6 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
@@ -13,7 +13,7 @@ public struct MixedPropertiesAndAdditionalPropertiesClass: Codable {
     public var dateTime: Date?
     public var map: [String: Animal]?
 
-    public init(uuid: UUID?, dateTime: Date?, map: [String: Animal]?) {
+    public init(uuid: UUID? = nil, dateTime: Date? = nil, map: [String: Animal]? = nil) {
         self.uuid = uuid
         self.dateTime = dateTime
         self.map = map
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
index b61db7d6e71..6365e8799f7 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
@@ -13,7 +13,7 @@ public struct Model200Response: Codable {
     public var name: Int?
     public var _class: String?
 
-    public init(name: Int?, _class: String?) {
+    public init(name: Int? = nil, _class: String? = nil) {
         self.name = name
         self._class = _class
     }
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Name.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
index 8ab4db44b73..5797209dce3 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
@@ -15,7 +15,7 @@ public struct Name: Codable {
     public var property: String?
     public var _123number: Int?
 
-    public init(name: Int, snakeCase: Int?, property: String?, _123number: Int?) {
+    public init(name: Int, snakeCase: Int? = nil, property: String? = nil, _123number: Int? = nil) {
         self.name = name
         self.snakeCase = snakeCase
         self.property = property
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
index 4d1dafcc2c1..979335c098b 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
@@ -11,7 +11,7 @@ public struct NumberOnly: Codable {
 
     public var justNumber: Double?
 
-    public init(justNumber: Double?) {
+    public init(justNumber: Double? = nil) {
         self.justNumber = justNumber
     }
 
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Order.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
index 40c30cc8609..f1817f7792a 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
@@ -22,7 +22,7 @@ public struct Order: Codable {
     public var status: Status?
     public var complete: Bool? = false
 
-    public init(id: Int64?, petId: Int64?, quantity: Int?, shipDate: Date?, status: Status?, complete: Bool?) {
+    public init(id: Int64? = nil, petId: Int64? = nil, quantity: Int? = nil, shipDate: Date? = nil, status: Status? = nil, complete: Bool? = nil) {
         self.id = id
         self.petId = petId
         self.quantity = quantity
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
index 18c3a024f12..d01e8da2166 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
@@ -13,7 +13,7 @@ public struct OuterComposite: Codable {
     public var myString: String?
     public var myBoolean: Bool?
 
-    public init(myNumber: Double?, myString: String?, myBoolean: Bool?) {
+    public init(myNumber: Double? = nil, myString: String? = nil, myBoolean: Bool? = nil) {
         self.myNumber = myNumber
         self.myString = myString
         self.myBoolean = myBoolean
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
index b9ce0e93325..caea19425d8 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
@@ -22,7 +22,7 @@ public struct Pet: Codable {
     /** pet status in the store */
     public var status: Status?
 
-    public init(id: Int64?, category: Category?, name: String, photoUrls: [String], tags: [Tag]?, status: Status?) {
+    public init(id: Int64? = nil, category: Category? = nil, name: String, photoUrls: [String], tags: [Tag]? = nil, status: Status? = nil) {
         self.id = id
         self.category = category
         self.name = name
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
index 0acd21fd100..f643334038e 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
@@ -12,7 +12,7 @@ public struct ReadOnlyFirst: Codable {
     public var bar: String?
     public var baz: String?
 
-    public init(bar: String?, baz: String?) {
+    public init(bar: String? = nil, baz: String? = nil) {
         self.bar = bar
         self.baz = baz
     }
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Return.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
index c223f993a69..45479e2b0de 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
@@ -12,7 +12,7 @@ public struct Return: Codable {
 
     public var _return: Int?
 
-    public init(_return: Int?) {
+    public init(_return: Int? = nil) {
         self._return = _return
     }
 
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
index 6e8650f76d8..8515496eb27 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
@@ -11,7 +11,7 @@ public struct SpecialModelName: Codable {
 
     public var specialPropertyName: Int64?
 
-    public init(specialPropertyName: Int64?) {
+    public init(specialPropertyName: Int64? = nil) {
         self.specialPropertyName = specialPropertyName
     }
 
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
index 4dd8a9a9f5a..82c02f04b69 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
@@ -12,7 +12,7 @@ public struct Tag: Codable {
     public var id: Int64?
     public var name: String?
 
-    public init(id: Int64?, name: String?) {
+    public init(id: Int64? = nil, name: String? = nil) {
         self.id = id
         self.name = name
     }
diff --git a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/User.swift b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/User.swift
index 79f271ed735..03e2736bd23 100644
--- a/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/User.swift
+++ b/samples/client/petstore/swift5/rxswiftLibrary/PetstoreClient/Classes/OpenAPIs/Models/User.swift
@@ -19,7 +19,7 @@ public struct User: Codable {
     /** User Status */
     public var userStatus: Int?
 
-    public init(id: Int64?, username: String?, firstName: String?, lastName: String?, email: String?, password: String?, phone: String?, userStatus: Int?) {
+    public init(id: Int64? = nil, username: String? = nil, firstName: String? = nil, lastName: String? = nil, email: String? = nil, password: String? = nil, phone: String? = nil, userStatus: Int? = nil) {
         self.id = id
         self.username = username
         self.firstName = firstName
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
index 1af03153596..81020425ad1 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/AdditionalPropertiesClass.swift
@@ -12,7 +12,7 @@ public struct AdditionalPropertiesClass: Codable {
     public var mapString: [String: String]?
     public var mapMapString: [String: [String: String]]?
 
-    public init(mapString: [String: String]?, mapMapString: [String: [String: String]]?) {
+    public init(mapString: [String: String]? = nil, mapMapString: [String: [String: String]]? = nil) {
         self.mapString = mapString
         self.mapMapString = mapMapString
     }
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
index 5ed9f31e2a3..c34ac85ac63 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Animal.swift
@@ -12,7 +12,7 @@ public struct Animal: Codable {
     public var className: String
     public var color: String? = "red"
 
-    public init(className: String, color: String?) {
+    public init(className: String, color: String? = nil) {
         self.className = className
         self.color = color
     }
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
index ec270da8907..6ad3d808a97 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/ApiResponse.swift
@@ -13,7 +13,7 @@ public struct ApiResponse: Codable {
     public var type: String?
     public var message: String?
 
-    public init(code: Int?, type: String?, message: String?) {
+    public init(code: Int? = nil, type: String? = nil, message: String? = nil) {
         self.code = code
         self.type = type
         self.message = message
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
index 6c252ed475b..6d99f90fdd1 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfArrayOfNumberOnly.swift
@@ -11,7 +11,7 @@ public struct ArrayOfArrayOfNumberOnly: Codable {
 
     public var arrayArrayNumber: [[Double]]?
 
-    public init(arrayArrayNumber: [[Double]]?) {
+    public init(arrayArrayNumber: [[Double]]? = nil) {
         self.arrayArrayNumber = arrayArrayNumber
     }
 
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
index e84eb5d6502..d59c529ef65 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayOfNumberOnly.swift
@@ -11,7 +11,7 @@ public struct ArrayOfNumberOnly: Codable {
 
     public var arrayNumber: [Double]?
 
-    public init(arrayNumber: [Double]?) {
+    public init(arrayNumber: [Double]? = nil) {
         self.arrayNumber = arrayNumber
     }
 
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
index d2140933d18..fdab67b0c59 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/ArrayTest.swift
@@ -13,7 +13,7 @@ public struct ArrayTest: Codable {
     public var arrayArrayOfInteger: [[Int64]]?
     public var arrayArrayOfModel: [[ReadOnlyFirst]]?
 
-    public init(arrayOfString: [String]?, arrayArrayOfInteger: [[Int64]]?, arrayArrayOfModel: [[ReadOnlyFirst]]?) {
+    public init(arrayOfString: [String]? = nil, arrayArrayOfInteger: [[Int64]]? = nil, arrayArrayOfModel: [[ReadOnlyFirst]]? = nil) {
         self.arrayOfString = arrayOfString
         self.arrayArrayOfInteger = arrayArrayOfInteger
         self.arrayArrayOfModel = arrayArrayOfModel
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
index d1b3b27616e..a7f8abe9719 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Capitalization.swift
@@ -17,7 +17,7 @@ public struct Capitalization: Codable {
     /** Name of the pet  */
     public var ATT_NAME: String?
 
-    public init(smallCamel: String?, capitalCamel: String?, smallSnake: String?, capitalSnake: String?, sCAETHFlowPoints: String?, ATT_NAME: String?) {
+    public init(smallCamel: String? = nil, capitalCamel: String? = nil, smallSnake: String? = nil, capitalSnake: String? = nil, sCAETHFlowPoints: String? = nil, ATT_NAME: String? = nil) {
         self.smallCamel = smallCamel
         self.capitalCamel = capitalCamel
         self.smallSnake = smallSnake
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
index 7ab887f3113..884020d1a72 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Cat.swift
@@ -13,7 +13,7 @@ public struct Cat: Codable {
     public var color: String? = "red"
     public var declawed: Bool?
 
-    public init(className: String, color: String?, declawed: Bool?) {
+    public init(className: String, color: String? = nil, declawed: Bool? = nil) {
         self.className = className
         self.color = color
         self.declawed = declawed
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
index a51ad0dffab..c7178efcb16 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/CatAllOf.swift
@@ -11,7 +11,7 @@ public struct CatAllOf: Codable {
 
     public var declawed: Bool?
 
-    public init(declawed: Bool?) {
+    public init(declawed: Bool? = nil) {
         self.declawed = declawed
     }
 
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Category.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
index eb8f7e5e197..78bf6826d69 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Category.swift
@@ -12,7 +12,7 @@ public struct Category: Codable {
     public var id: Int64?
     public var name: String = "default-name"
 
-    public init(id: Int64?, name: String) {
+    public init(id: Int64? = nil, name: String) {
         self.id = id
         self.name = name
     }
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
index e2a7d4427a0..d7299a05856 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/ClassModel.swift
@@ -12,7 +12,7 @@ public struct ClassModel: Codable {
 
     public var _class: String?
 
-    public init(_class: String?) {
+    public init(_class: String? = nil) {
         self._class = _class
     }
 
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Client.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
index 00245ca3728..c8e0b51314d 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Client.swift
@@ -11,7 +11,7 @@ public struct Client: Codable {
 
     public var client: String?
 
-    public init(client: String?) {
+    public init(client: String? = nil) {
         self.client = client
     }
 
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
index 492c1228008..e7e0efa931e 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Dog.swift
@@ -13,7 +13,7 @@ public struct Dog: Codable {
     public var color: String? = "red"
     public var breed: String?
 
-    public init(className: String, color: String?, breed: String?) {
+    public init(className: String, color: String? = nil, breed: String? = nil) {
         self.className = className
         self.color = color
         self.breed = breed
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
index 7786f8acc5a..1f61ed3c343 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/DogAllOf.swift
@@ -11,7 +11,7 @@ public struct DogAllOf: Codable {
 
     public var breed: String?
 
-    public init(breed: String?) {
+    public init(breed: String? = nil) {
         self.breed = breed
     }
 
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
index 9844e7c40e3..10536376ccc 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumArrays.swift
@@ -20,7 +20,7 @@ public struct EnumArrays: Codable {
     public var justSymbol: JustSymbol?
     public var arrayEnum: [ArrayEnum]?
 
-    public init(justSymbol: JustSymbol?, arrayEnum: [ArrayEnum]?) {
+    public init(justSymbol: JustSymbol? = nil, arrayEnum: [ArrayEnum]? = nil) {
         self.justSymbol = justSymbol
         self.arrayEnum = arrayEnum
     }
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
index 789f583e1d7..c0d7c84b69d 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/EnumTest.swift
@@ -33,7 +33,7 @@ public struct EnumTest: Codable {
     public var enumNumber: EnumNumber?
     public var outerEnum: OuterEnum?
 
-    public init(enumString: EnumString?, enumStringRequired: EnumStringRequired, enumInteger: EnumInteger?, enumNumber: EnumNumber?, outerEnum: OuterEnum?) {
+    public init(enumString: EnumString? = nil, enumStringRequired: EnumStringRequired, enumInteger: EnumInteger? = nil, enumNumber: EnumNumber? = nil, outerEnum: OuterEnum? = nil) {
         self.enumString = enumString
         self.enumStringRequired = enumStringRequired
         self.enumInteger = enumInteger
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/File.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/File.swift
index abf3ccffc48..54ffb6e70e3 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/File.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/File.swift
@@ -13,7 +13,7 @@ public struct File: Codable {
     /** Test capitalization */
     public var sourceURI: String?
 
-    public init(sourceURI: String?) {
+    public init(sourceURI: String? = nil) {
         self.sourceURI = sourceURI
     }
 
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
index 532f1457939..3d70ffe0a59 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/FileSchemaTestClass.swift
@@ -12,7 +12,7 @@ public struct FileSchemaTestClass: Codable {
     public var file: File?
     public var files: [File]?
 
-    public init(file: File?, files: [File]?) {
+    public init(file: File? = nil, files: [File]? = nil) {
         self.file = file
         self.files = files
     }
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
index 20bd6d103b3..c934df71b34 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/FormatTest.swift
@@ -23,7 +23,7 @@ public struct FormatTest: Codable {
     public var uuid: UUID?
     public var password: String
 
-    public init(integer: Int?, int32: Int?, int64: Int64?, number: Double, float: Float?, double: Double?, string: String?, byte: Data, binary: URL?, date: Date, dateTime: Date?, uuid: UUID?, password: String) {
+    public init(integer: Int? = nil, int32: Int? = nil, int64: Int64? = nil, number: Double, float: Float? = nil, double: Double? = nil, string: String? = nil, byte: Data, binary: URL? = nil, date: Date, dateTime: Date? = nil, uuid: UUID? = nil, password: String) {
         self.integer = integer
         self.int32 = int32
         self.int64 = int64
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
index 906ddb06fb1..a6d3567e885 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/HasOnlyReadOnly.swift
@@ -12,7 +12,7 @@ public struct HasOnlyReadOnly: Codable {
     public var bar: String?
     public var foo: String?
 
-    public init(bar: String?, foo: String?) {
+    public init(bar: String? = nil, foo: String? = nil) {
         self.bar = bar
         self.foo = foo
     }
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/List.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/List.swift
index fe13d302ccb..6de49531ac1 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/List.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/List.swift
@@ -11,7 +11,7 @@ public struct List: Codable {
 
     public var _123list: String?
 
-    public init(_123list: String?) {
+    public init(_123list: String? = nil) {
         self._123list = _123list
     }
 
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
index 4b6037f378e..a9762da6155 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/MapTest.swift
@@ -18,7 +18,7 @@ public struct MapTest: Codable {
     public var directMap: [String: Bool]?
     public var indirectMap: StringBooleanMap?
 
-    public init(mapMapOfString: [String: [String: String]]?, mapOfEnumString: [String: String]?, directMap: [String: Bool]?, indirectMap: StringBooleanMap?) {
+    public init(mapMapOfString: [String: [String: String]]? = nil, mapOfEnumString: [String: String]? = nil, directMap: [String: Bool]? = nil, indirectMap: StringBooleanMap? = nil) {
         self.mapMapOfString = mapMapOfString
         self.mapOfEnumString = mapOfEnumString
         self.directMap = directMap
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
index c3deb2f2893..f1d081064b6 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/MixedPropertiesAndAdditionalPropertiesClass.swift
@@ -13,7 +13,7 @@ public struct MixedPropertiesAndAdditionalPropertiesClass: Codable {
     public var dateTime: Date?
     public var map: [String: Animal]?
 
-    public init(uuid: UUID?, dateTime: Date?, map: [String: Animal]?) {
+    public init(uuid: UUID? = nil, dateTime: Date? = nil, map: [String: Animal]? = nil) {
         self.uuid = uuid
         self.dateTime = dateTime
         self.map = map
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
index b61db7d6e71..6365e8799f7 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Model200Response.swift
@@ -13,7 +13,7 @@ public struct Model200Response: Codable {
     public var name: Int?
     public var _class: String?
 
-    public init(name: Int?, _class: String?) {
+    public init(name: Int? = nil, _class: String? = nil) {
         self.name = name
         self._class = _class
     }
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Name.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
index 8ab4db44b73..5797209dce3 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Name.swift
@@ -15,7 +15,7 @@ public struct Name: Codable {
     public var property: String?
     public var _123number: Int?
 
-    public init(name: Int, snakeCase: Int?, property: String?, _123number: Int?) {
+    public init(name: Int, snakeCase: Int? = nil, property: String? = nil, _123number: Int? = nil) {
         self.name = name
         self.snakeCase = snakeCase
         self.property = property
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
index 4d1dafcc2c1..979335c098b 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/NumberOnly.swift
@@ -11,7 +11,7 @@ public struct NumberOnly: Codable {
 
     public var justNumber: Double?
 
-    public init(justNumber: Double?) {
+    public init(justNumber: Double? = nil) {
         self.justNumber = justNumber
     }
 
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Order.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
index 40c30cc8609..f1817f7792a 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Order.swift
@@ -22,7 +22,7 @@ public struct Order: Codable {
     public var status: Status?
     public var complete: Bool? = false
 
-    public init(id: Int64?, petId: Int64?, quantity: Int?, shipDate: Date?, status: Status?, complete: Bool?) {
+    public init(id: Int64? = nil, petId: Int64? = nil, quantity: Int? = nil, shipDate: Date? = nil, status: Status? = nil, complete: Bool? = nil) {
         self.id = id
         self.petId = petId
         self.quantity = quantity
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
index 18c3a024f12..d01e8da2166 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/OuterComposite.swift
@@ -13,7 +13,7 @@ public struct OuterComposite: Codable {
     public var myString: String?
     public var myBoolean: Bool?
 
-    public init(myNumber: Double?, myString: String?, myBoolean: Bool?) {
+    public init(myNumber: Double? = nil, myString: String? = nil, myBoolean: Bool? = nil) {
         self.myNumber = myNumber
         self.myString = myString
         self.myBoolean = myBoolean
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
index b9ce0e93325..caea19425d8 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Pet.swift
@@ -22,7 +22,7 @@ public struct Pet: Codable {
     /** pet status in the store */
     public var status: Status?
 
-    public init(id: Int64?, category: Category?, name: String, photoUrls: [String], tags: [Tag]?, status: Status?) {
+    public init(id: Int64? = nil, category: Category? = nil, name: String, photoUrls: [String], tags: [Tag]? = nil, status: Status? = nil) {
         self.id = id
         self.category = category
         self.name = name
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
index 0acd21fd100..f643334038e 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/ReadOnlyFirst.swift
@@ -12,7 +12,7 @@ public struct ReadOnlyFirst: Codable {
     public var bar: String?
     public var baz: String?
 
-    public init(bar: String?, baz: String?) {
+    public init(bar: String? = nil, baz: String? = nil) {
         self.bar = bar
         self.baz = baz
     }
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Return.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
index c223f993a69..45479e2b0de 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Return.swift
@@ -12,7 +12,7 @@ public struct Return: Codable {
 
     public var _return: Int?
 
-    public init(_return: Int?) {
+    public init(_return: Int? = nil) {
         self._return = _return
     }
 
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
index 6e8650f76d8..8515496eb27 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/SpecialModelName.swift
@@ -11,7 +11,7 @@ public struct SpecialModelName: Codable {
 
     public var specialPropertyName: Int64?
 
-    public init(specialPropertyName: Int64?) {
+    public init(specialPropertyName: Int64? = nil) {
         self.specialPropertyName = specialPropertyName
     }
 
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
index 4dd8a9a9f5a..82c02f04b69 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/Tag.swift
@@ -12,7 +12,7 @@ public struct Tag: Codable {
     public var id: Int64?
     public var name: String?
 
-    public init(id: Int64?, name: String?) {
+    public init(id: Int64? = nil, name: String? = nil) {
         self.id = id
         self.name = name
     }
diff --git a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/User.swift b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/User.swift
index 79f271ed735..03e2736bd23 100644
--- a/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/User.swift
+++ b/samples/client/petstore/swift5/urlsessionLibrary/PetstoreClient/Classes/OpenAPIs/Models/User.swift
@@ -19,7 +19,7 @@ public struct User: Codable {
     /** User Status */
     public var userStatus: Int?
 
-    public init(id: Int64?, username: String?, firstName: String?, lastName: String?, email: String?, password: String?, phone: String?, userStatus: Int?) {
+    public init(id: Int64? = nil, username: String? = nil, firstName: String? = nil, lastName: String? = nil, email: String? = nil, password: String? = nil, phone: String? = nil, userStatus: Int? = nil) {
         self.id = id
         self.username = username
         self.firstName = firstName