diff --git a/modules/openapi-generator/src/main/resources/crystal/partial_model_generic.mustache b/modules/openapi-generator/src/main/resources/crystal/partial_model_generic.mustache
index 4f2de178b0e..8e09ec2aba3 100644
--- a/modules/openapi-generator/src/main/resources/crystal/partial_model_generic.mustache
+++ b/modules/openapi-generator/src/main/resources/crystal/partial_model_generic.mustache
@@ -4,14 +4,28 @@
   class {{classname}}{{#parent}} < {{{.}}}{{/parent}}
     include JSON::Serializable
 
-    {{#vars}}
+    {{#hasRequired}}
+    # Required properties
+    {{/hasRequired}}
+    {{#requiredVars}}
     {{#description}}
     # {{{.}}}
     {{/description}}
-    @[JSON::Field(key: "{{{baseName}}}", type: {{{dataType}}}{{#defaultValue}}, default: {{{defaultValue}}}{{/defaultValue}}{{#isNullable}}, nillable: true, emit_null: true{{/isNullable}})]
+    @[JSON::Field(key: "{{{baseName}}}", type: {{{dataType}}}{{#defaultValue}}, default: {{{defaultValue}}}{{/defaultValue}}, nillable: false, emit_null: false)]
     property {{{name}}} : {{{dataType}}}
 
-  {{/vars}}
+    {{/requiredVars}}
+    {{#hasOptional}}
+    # Optional properties
+    {{/hasOptional}}
+    {{#optionalVars}}
+    {{#description}}
+    # {{{.}}}
+    {{/description}}
+    @[JSON::Field(key: "{{{baseName}}}", type: {{{dataType}}}?{{#defaultValue}}, default: {{{defaultValue}}}{{/defaultValue}}, nillable: true, emit_null: false)]
+    property {{{name}}} : {{{dataType}}}?
+
+    {{/optionalVars}}
 {{#hasEnums}}
     class EnumAttributeValidator
       getter datatype : String
@@ -74,7 +88,7 @@
     {{/discriminator}}
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
-    def initialize({{#vars}}@{{{name}}} : {{{dataType}}}{{^required}}?{{/required}}{{^-last}}, {{/-last}}{{/vars}})
+    def initialize({{#requiredVars}}@{{{name}}} : {{{dataType}}}{{^-last}}, {{/-last}}{{/requiredVars}}{{#hasRequired}}{{#hasOptional}}, {{/hasOptional}}{{/hasRequired}}{{#optionalVars}}@{{{name}}} : {{{dataType}}}?{{^-last}}, {{/-last}}{{/optionalVars}})
     end
 
     # Show invalid properties with the reasons. Usually used together with valid?
@@ -82,14 +96,6 @@
     def list_invalid_properties
       invalid_properties = {{^parent}}Array(String).new{{/parent}}{{#parent}}super{{/parent}}
       {{#vars}}
-      {{^isNullable}}
-      {{#required}}
-      if @{{{name}}}.nil?
-        invalid_properties.push("invalid value for \"{{{name}}}\", {{{name}}} cannot be nil.")
-      end
-
-      {{/required}}
-      {{/isNullable}}
       {{#hasValidation}}
       {{#maxLength}}
       if {{^required}}!@{{{name}}}.nil? && {{/required}}@{{{name}}}.to_s.size > {{{maxLength}}}
@@ -143,11 +149,6 @@
     # @return true if the model is valid
     def valid?
       {{#vars}}
-      {{^isNullable}}
-      {{#required}}
-      return false if @{{{name}}}.nil?
-      {{/required}}
-      {{/isNullable}}
       {{#isEnum}}
       {{^isContainer}}
       {{{name}}}_validator = EnumAttributeValidator.new("{{{dataType}}}", [{{#allowableValues}}{{#enumVars}}{{{value}}}{{^-last}}, {{/-last}}{{/enumVars}}{{/allowableValues}}])
@@ -217,14 +218,6 @@
     # Custom attribute writer method with validation
     # @param [Object] {{{name}}} Value to be assigned
     def {{{name}}}=({{{name}}})
-      {{^isNullable}}
-      {{#required}}
-      if {{{name}}}.nil?
-        raise ArgumentError.new("{{{name}}} cannot be nil")
-      end
-
-      {{/required}}
-      {{/isNullable}}
       {{#maxLength}}
       if {{^required}}!{{{name}}}.nil? && {{/required}}{{{name}}}.to_s.size > {{{maxLength}}}
         raise ArgumentError.new("invalid value for \"{{{name}}}\", the character length must be smaller than or equal to {{{maxLength}}}.")
@@ -277,7 +270,7 @@
     # Checks equality by comparing each attribute.
     # @param [Object] Object to be compared
     def ==(o)
-      return true if self.equal?(o)
+      return true if self.same?(o)
       self.class == o.class{{#vars}} &&
           {{name}} == o.{{name}}{{/vars}}{{#parent}} && super(o){{/parent}}
     end
diff --git a/modules/openapi-generator/src/main/resources/crystal/spec_helper.mustache b/modules/openapi-generator/src/main/resources/crystal/spec_helper.mustache
index 9facafa4a93..56675bb6876 100644
--- a/modules/openapi-generator/src/main/resources/crystal/spec_helper.mustache
+++ b/modules/openapi-generator/src/main/resources/crystal/spec_helper.mustache
@@ -3,4 +3,12 @@
 # load modules
 require "spec"
 require "json"
-require "../src/{{{shardName}}}"
\ No newline at end of file
+require "../src/{{{shardName}}}"
+
+def assert_compilation_error(path : String, message : String) : Nil
+  buffer = IO::Memory.new
+  result = Process.run("crystal", ["run", "--no-color", "--no-codegen", path], error: buffer)
+  result.success?.should be_false
+  buffer.to_s.should contain message
+  buffer.close
+end
diff --git a/samples/client/petstore/crystal/pet_compilation_error_spec.cr b/samples/client/petstore/crystal/pet_compilation_error_spec.cr
new file mode 100644
index 00000000000..519cb5b73e3
--- /dev/null
+++ b/samples/client/petstore/crystal/pet_compilation_error_spec.cr
@@ -0,0 +1,11 @@
+require "./spec/spec_helper"
+require "json"
+require "time"
+
+describe Petstore::Pet do
+  describe "test an instance of Pet" do
+    it "should fail to compile if any required properties is missing" do
+      pet = Petstore::Pet.new(id: nil, category: nil, name: nil, photo_urls: Array(String).new, tags: nil, status: nil)
+    end
+  end
+end
diff --git a/samples/client/petstore/crystal/spec/api/pet_api_spec.cr b/samples/client/petstore/crystal/spec/api/pet_api_spec.cr
index 5c5f56295ac..5eb508ebd72 100644
--- a/samples/client/petstore/crystal/spec/api/pet_api_spec.cr
+++ b/samples/client/petstore/crystal/spec/api/pet_api_spec.cr
@@ -29,8 +29,28 @@ describe "PetApi" do
   # @param [Hash] opts the optional parameters
   # @return [Pet]
   describe "add_pet test" do
-    it "should work" do
+    it "should work with only required attributes" do
       # assertion here. ref: https://crystal-lang.org/reference/guides/testing.html
+
+      config = Petstore::Configuration.new
+      config.access_token = "yyy"
+      config.api_key[:api_key] = "xxx"
+      config.api_key_prefix[:api_key] = "Token"
+
+      api_client = Petstore::ApiClient.new(config)
+
+      api_instance = Petstore::PetApi.new(api_client)
+
+      pet_name = "new pet"
+      new_pet = Petstore::Pet.new(id: nil, category: nil, name: pet_name, photo_urls: Array(String).new, tags: nil, status: nil)
+
+      pet = api_instance.add_pet(new_pet)
+      pet.id.should_not be_nil
+      pet.category.should be_nil
+      pet.name.should eq pet_name
+      pet.photo_urls.should eq Array(String).new
+      pet.status.should be_nil
+      pet.tags.should eq Array(Petstore::Tag).new
     end
   end
 
@@ -89,20 +109,17 @@ describe "PetApi" do
 
       api_instance = Petstore::PetApi.new(api_client)
 
-      # create a pet to start with
-      pet_id = Int64.new(91829)
-      pet = Petstore::Pet.new(id: pet_id, category: Petstore::Category.new(id: pet_id + 10, name: "crystal category"), name: "crystal", photo_urls: ["https://crystal-lang.org"], tags: [Petstore::Tag.new(id: pet_id + 100, name: "crystal tag")], status: "available")
-
-      api_instance.add_pet(pet)
+      new_pet = Petstore::Pet.new(id: nil, category: nil, name: "crystal", photo_urls: Array(String).new, tags: nil, status: nil)
 
+      pet = api_instance.add_pet(new_pet)
+      pet_id = pet.id.not_nil!
       result = api_instance.get_pet_by_id(pet_id: pet_id)
       result.id.should eq pet_id
-      result.category.id.should eq pet_id + 10
-      result.category.name.should eq "crystal category"
+      result.category.should be_nil
       result.name.should eq "crystal"
-      result.photo_urls.should eq ["https://crystal-lang.org"]
-      result.status.should eq "available" 
-      result.tags[0].id.should eq pet_id + 100
+      result.photo_urls.should eq Array(String).new
+      result.status.should be_nil
+      result.tags.should eq Array(Petstore::Tag).new
     end
   end
 
diff --git a/samples/client/petstore/crystal/spec/models/pet_spec.cr b/samples/client/petstore/crystal/spec/models/pet_spec.cr
index d3eaf60dfc1..16117449db5 100644
--- a/samples/client/petstore/crystal/spec/models/pet_spec.cr
+++ b/samples/client/petstore/crystal/spec/models/pet_spec.cr
@@ -18,11 +18,49 @@ require "time"
 describe Petstore::Pet do
 
   describe "test an instance of Pet" do
-    it "should create an instance of Pet" do
-      #instance = Petstore::Pet.new
-      #expect(instance).to be_instance_of(Petstore::Pet)
+    it "should fail to compile if any required properties is missing" do
+      assert_compilation_error(path: "./pet_compilation_error_spec.cr", message: "Error: no overload matches 'Petstore::Pet.new', id: Nil, category: Nil, name: Nil, photo_urls: Array(String), tags: Nil, status: Nil")
+    end
+
+    it "should create an instance of Pet with only required properties" do
+      pet = Petstore::Pet.new(id: nil, category: nil, name: "new pet", photo_urls: Array(String).new, tags: nil, status: nil)
+      pet.should be_a(Petstore::Pet)
+    end
+
+    it "should create an instance of Pet with all properties" do
+      pet_id = 12345_i64
+      pet = Petstore::Pet.new(id: pet_id, category: Petstore::Category.new(id: pet_id + 10, name: "crystal category"), name: "crystal", photo_urls: ["https://crystal-lang.org"], tags: [Petstore::Tag.new(id: pet_id + 100, name: "crystal tag")], status: "available")
+      pet.should be_a(Petstore::Pet)
     end
   end
+
+  describe "#from_json" do
+    it "should instantiate a new instance from json string with required properties" do
+      pet = Petstore::Pet.from_json("{\"name\": \"json pet\", \"photoUrls\": []}")
+      pet.should be_a(Petstore::Pet)
+      pet.name.should eq "json pet"
+      pet.photo_urls.should eq Array(String).new
+    end
+
+    it "should raise error when instantiating a new instance from json string with missing required properties" do
+      expect_raises(JSON::SerializableError, "Missing JSON attribute: name") do
+        Petstore::Pet.from_json("{\"photoUrls\": []}")
+      end
+      expect_raises(JSON::SerializableError, "Missing JSON attribute: photoUrls") do
+        Petstore::Pet.from_json("{\"name\": \"json pet\"}")
+      end
+    end
+
+    it "should raise error when instantiating a new instance from json string with required properties set to null value" do
+      expect_raises(JSON::SerializableError, "Expected String but was Null") do
+        Petstore::Pet.from_json("{\"name\": null, \"photoUrls\": []}")
+      end
+      expect_raises(JSON::SerializableError, "Expected BeginArray but was Null") do
+        Petstore::Pet.from_json("{\"name\": \"json pet\", \"photoUrls\": null}")
+      end
+    end
+  end
+
   describe "test attribute 'id'" do
     it "should work" do
       # assertion here. ref: https://crystal-lang.org/reference/guides/testing.html
diff --git a/samples/client/petstore/crystal/spec/models/tag_spec.cr b/samples/client/petstore/crystal/spec/models/tag_spec.cr
index f79e12657fc..64a05f292ce 100644
--- a/samples/client/petstore/crystal/spec/models/tag_spec.cr
+++ b/samples/client/petstore/crystal/spec/models/tag_spec.cr
@@ -23,6 +23,21 @@ describe Petstore::Tag do
       #expect(instance).to be_instance_of(Petstore::Tag)
     end
   end
+
+  describe "test equality of Tag instances" do
+    it "should equal to itself" do
+      tag1 = Petstore::Tag.new(id: 0, name: "same")
+      tag2 = tag1
+      (tag1 == tag2).should be_true
+    end
+
+    it "should equal to another instance with same attributes" do
+      tag1 = Petstore::Tag.new(id: 0, name: "tag")
+      tag2 = Petstore::Tag.new(id: 0, name: "tag")
+      (tag1 == tag2).should be_true
+    end
+  end
+
   describe "test attribute 'id'" do
     it "should work" do
       # assertion here. ref: https://crystal-lang.org/reference/guides/testing.html
diff --git a/samples/client/petstore/crystal/spec/spec_helper.cr b/samples/client/petstore/crystal/spec/spec_helper.cr
index c6eb4e7a603..7349161df1e 100644
--- a/samples/client/petstore/crystal/spec/spec_helper.cr
+++ b/samples/client/petstore/crystal/spec/spec_helper.cr
@@ -11,4 +11,12 @@
 # load modules
 require "spec"
 require "json"
-require "../src/petstore"
\ No newline at end of file
+require "../src/petstore"
+
+def assert_compilation_error(path : String, message : String) : Nil
+  buffer = IO::Memory.new
+  result = Process.run("crystal", ["run", "--no-color", "--no-codegen", path], error: buffer)
+  result.success?.should be_false
+  buffer.to_s.should contain message
+  buffer.close
+end
diff --git a/samples/client/petstore/crystal/src/petstore/models/api_response.cr b/samples/client/petstore/crystal/src/petstore/models/api_response.cr
index be551134907..7a0719b6615 100644
--- a/samples/client/petstore/crystal/src/petstore/models/api_response.cr
+++ b/samples/client/petstore/crystal/src/petstore/models/api_response.cr
@@ -16,14 +16,15 @@ module Petstore
   class ApiResponse
     include JSON::Serializable
 
-    @[JSON::Field(key: "code", type: Int32)]
-    property code : Int32
+    # Optional properties
+    @[JSON::Field(key: "code", type: Int32?, nillable: true, emit_null: false)]
+    property code : Int32?
 
-    @[JSON::Field(key: "type", type: String)]
-    property _type : String
+    @[JSON::Field(key: "type", type: String?, nillable: true, emit_null: false)]
+    property _type : String?
 
-    @[JSON::Field(key: "message", type: String)]
-    property message : String
+    @[JSON::Field(key: "message", type: String?, nillable: true, emit_null: false)]
+    property message : String?
 
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
@@ -46,7 +47,7 @@ module Petstore
     # Checks equality by comparing each attribute.
     # @param [Object] Object to be compared
     def ==(o)
-      return true if self.equal?(o)
+      return true if self.same?(o)
       self.class == o.class &&
           code == o.code &&
           _type == o._type &&
diff --git a/samples/client/petstore/crystal/src/petstore/models/category.cr b/samples/client/petstore/crystal/src/petstore/models/category.cr
index 55c64154d97..65dd3f8cdd0 100644
--- a/samples/client/petstore/crystal/src/petstore/models/category.cr
+++ b/samples/client/petstore/crystal/src/petstore/models/category.cr
@@ -16,11 +16,12 @@ module Petstore
   class Category
     include JSON::Serializable
 
-    @[JSON::Field(key: "id", type: Int64)]
-    property id : Int64
+    # Optional properties
+    @[JSON::Field(key: "id", type: Int64?, nillable: true, emit_null: false)]
+    property id : Int64?
 
-    @[JSON::Field(key: "name", type: String)]
-    property name : String
+    @[JSON::Field(key: "name", type: String?, nillable: true, emit_null: false)]
+    property name : String?
 
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
@@ -60,7 +61,7 @@ module Petstore
     # Checks equality by comparing each attribute.
     # @param [Object] Object to be compared
     def ==(o)
-      return true if self.equal?(o)
+      return true if self.same?(o)
       self.class == o.class &&
           id == o.id &&
           name == o.name
diff --git a/samples/client/petstore/crystal/src/petstore/models/order.cr b/samples/client/petstore/crystal/src/petstore/models/order.cr
index 5d00ea6688f..0536a0c3de6 100644
--- a/samples/client/petstore/crystal/src/petstore/models/order.cr
+++ b/samples/client/petstore/crystal/src/petstore/models/order.cr
@@ -16,24 +16,25 @@ module Petstore
   class Order
     include JSON::Serializable
 
-    @[JSON::Field(key: "id", type: Int64)]
-    property id : Int64
+    # Optional properties
+    @[JSON::Field(key: "id", type: Int64?, nillable: true, emit_null: false)]
+    property id : Int64?
 
-    @[JSON::Field(key: "petId", type: Int64)]
-    property pet_id : Int64
+    @[JSON::Field(key: "petId", type: Int64?, nillable: true, emit_null: false)]
+    property pet_id : Int64?
 
-    @[JSON::Field(key: "quantity", type: Int32)]
-    property quantity : Int32
+    @[JSON::Field(key: "quantity", type: Int32?, nillable: true, emit_null: false)]
+    property quantity : Int32?
 
-    @[JSON::Field(key: "shipDate", type: Time)]
-    property ship_date : Time
+    @[JSON::Field(key: "shipDate", type: Time?, nillable: true, emit_null: false)]
+    property ship_date : Time?
 
     # Order Status
-    @[JSON::Field(key: "status", type: String)]
-    property status : String
+    @[JSON::Field(key: "status", type: String?, nillable: true, emit_null: false)]
+    property status : String?
 
-    @[JSON::Field(key: "complete", type: Bool, default: false)]
-    property complete : Bool
+    @[JSON::Field(key: "complete", type: Bool?, default: false, nillable: true, emit_null: false)]
+    property complete : Bool?
 
     class EnumAttributeValidator
       getter datatype : String
@@ -91,7 +92,7 @@ module Petstore
     # Checks equality by comparing each attribute.
     # @param [Object] Object to be compared
     def ==(o)
-      return true if self.equal?(o)
+      return true if self.same?(o)
       self.class == o.class &&
           id == o.id &&
           pet_id == o.pet_id &&
diff --git a/samples/client/petstore/crystal/src/petstore/models/pet.cr b/samples/client/petstore/crystal/src/petstore/models/pet.cr
index cdac65776d7..8edf5789c9a 100644
--- a/samples/client/petstore/crystal/src/petstore/models/pet.cr
+++ b/samples/client/petstore/crystal/src/petstore/models/pet.cr
@@ -16,24 +16,26 @@ module Petstore
   class Pet
     include JSON::Serializable
 
-    @[JSON::Field(key: "id", type: Int64)]
-    property id : Int64
-
-    @[JSON::Field(key: "category", type: Category)]
-    property category : Category
-
-    @[JSON::Field(key: "name", type: String)]
+    # Required properties
+    @[JSON::Field(key: "name", type: String, nillable: false, emit_null: false)]
     property name : String
 
-    @[JSON::Field(key: "photoUrls", type: Array(String))]
+    @[JSON::Field(key: "photoUrls", type: Array(String), nillable: false, emit_null: false)]
     property photo_urls : Array(String)
 
-    @[JSON::Field(key: "tags", type: Array(Tag))]
-    property tags : Array(Tag)
+    # Optional properties
+    @[JSON::Field(key: "id", type: Int64?, nillable: true, emit_null: false)]
+    property id : Int64?
+
+    @[JSON::Field(key: "category", type: Category?, nillable: true, emit_null: false)]
+    property category : Category?
+
+    @[JSON::Field(key: "tags", type: Array(Tag)?, nillable: true, emit_null: false)]
+    property tags : Array(Tag)?
 
     # pet status in the store
-    @[JSON::Field(key: "status", type: String)]
-    property status : String
+    @[JSON::Field(key: "status", type: String?, nillable: true, emit_null: false)]
+    property status : String?
 
     class EnumAttributeValidator
       getter datatype : String
@@ -60,29 +62,19 @@ module Petstore
 
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
-    def initialize(@id : Int64?, @category : Category?, @name : String, @photo_urls : Array(String), @tags : Array(Tag)?, @status : String?)
+    def initialize(@name : String, @photo_urls : Array(String), @id : Int64?, @category : Category?, @tags : Array(Tag)?, @status : String?)
     end
 
     # Show invalid properties with the reasons. Usually used together with valid?
     # @return Array for valid properties with the reasons
     def list_invalid_properties
       invalid_properties = Array(String).new
-      if @name.nil?
-        invalid_properties.push("invalid value for \"name\", name cannot be nil.")
-      end
-
-      if @photo_urls.nil?
-        invalid_properties.push("invalid value for \"photo_urls\", photo_urls cannot be nil.")
-      end
-
       invalid_properties
     end
 
     # Check to see if the all the properties in the model are valid
     # @return true if the model is valid
     def valid?
-      return false if @name.nil?
-      return false if @photo_urls.nil?
       status_validator = EnumAttributeValidator.new("String", ["available", "pending", "sold"])
       return false unless status_validator.valid?(@status)
       true
@@ -101,7 +93,7 @@ module Petstore
     # Checks equality by comparing each attribute.
     # @param [Object] Object to be compared
     def ==(o)
-      return true if self.equal?(o)
+      return true if self.same?(o)
       self.class == o.class &&
           id == o.id &&
           category == o.category &&
diff --git a/samples/client/petstore/crystal/src/petstore/models/tag.cr b/samples/client/petstore/crystal/src/petstore/models/tag.cr
index bd293329185..cd5e7ed2989 100644
--- a/samples/client/petstore/crystal/src/petstore/models/tag.cr
+++ b/samples/client/petstore/crystal/src/petstore/models/tag.cr
@@ -16,11 +16,12 @@ module Petstore
   class Tag
     include JSON::Serializable
 
-    @[JSON::Field(key: "id", type: Int64)]
-    property id : Int64
+    # Optional properties
+    @[JSON::Field(key: "id", type: Int64?, nillable: true, emit_null: false)]
+    property id : Int64?
 
-    @[JSON::Field(key: "name", type: String)]
-    property name : String
+    @[JSON::Field(key: "name", type: String?, nillable: true, emit_null: false)]
+    property name : String?
 
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
@@ -43,7 +44,7 @@ module Petstore
     # Checks equality by comparing each attribute.
     # @param [Object] Object to be compared
     def ==(o)
-      return true if self.equal?(o)
+      return true if self.same?(o)
       self.class == o.class &&
           id == o.id &&
           name == o.name
diff --git a/samples/client/petstore/crystal/src/petstore/models/user.cr b/samples/client/petstore/crystal/src/petstore/models/user.cr
index 47430b4452a..a80b2574d2c 100644
--- a/samples/client/petstore/crystal/src/petstore/models/user.cr
+++ b/samples/client/petstore/crystal/src/petstore/models/user.cr
@@ -16,30 +16,31 @@ module Petstore
   class User
     include JSON::Serializable
 
-    @[JSON::Field(key: "id", type: Int64)]
-    property id : Int64
+    # Optional properties
+    @[JSON::Field(key: "id", type: Int64?, nillable: true, emit_null: false)]
+    property id : Int64?
 
-    @[JSON::Field(key: "username", type: String)]
-    property username : String
+    @[JSON::Field(key: "username", type: String?, nillable: true, emit_null: false)]
+    property username : String?
 
-    @[JSON::Field(key: "firstName", type: String)]
-    property first_name : String
+    @[JSON::Field(key: "firstName", type: String?, nillable: true, emit_null: false)]
+    property first_name : String?
 
-    @[JSON::Field(key: "lastName", type: String)]
-    property last_name : String
+    @[JSON::Field(key: "lastName", type: String?, nillable: true, emit_null: false)]
+    property last_name : String?
 
-    @[JSON::Field(key: "email", type: String)]
-    property email : String
+    @[JSON::Field(key: "email", type: String?, nillable: true, emit_null: false)]
+    property email : String?
 
-    @[JSON::Field(key: "password", type: String)]
-    property password : String
+    @[JSON::Field(key: "password", type: String?, nillable: true, emit_null: false)]
+    property password : String?
 
-    @[JSON::Field(key: "phone", type: String)]
-    property phone : String
+    @[JSON::Field(key: "phone", type: String?, nillable: true, emit_null: false)]
+    property phone : String?
 
     # User Status
-    @[JSON::Field(key: "userStatus", type: Int32)]
-    property user_status : Int32
+    @[JSON::Field(key: "userStatus", type: Int32?, nillable: true, emit_null: false)]
+    property user_status : Int32?
 
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
@@ -62,7 +63,7 @@ module Petstore
     # Checks equality by comparing each attribute.
     # @param [Object] Object to be compared
     def ==(o)
-      return true if self.equal?(o)
+      return true if self.same?(o)
       self.class == o.class &&
           id == o.id &&
           username == o.username &&