diff --git a/modules/swagger-codegen/src/main/resources/objc/SWGApiClient.m b/modules/swagger-codegen/src/main/resources/objc/SWGApiClient.m
index 4547e61277ab..15dbee074594 100644
--- a/modules/swagger-codegen/src/main/resources/objc/SWGApiClient.m
+++ b/modules/swagger-codegen/src/main/resources/objc/SWGApiClient.m
@@ -80,41 +80,48 @@ static bool loggingEnabled = true;
 }
 
 /*
- * Detect `Accept` from acceptArray
+ * Detect `Accept` from accepts
  */
-+ (NSString *) selectHeaderAccept:(NSArray *)acceptArray
++ (NSString *) selectHeaderAccept:(NSArray *)accepts
 {
-    // if acceptArray is nil or empty, return `application/json`
-    if (acceptArray == nil || [acceptArray count] == 0) {
-        return @"application/json";
+    if (accepts == nil || [accepts count] == 0) {
+        return @"";
     }
+    
+    NSMutableArray *lowerAccepts = [[NSMutableArray alloc] initWithCapacity:[accepts count]];
+    [accepts enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
+        [lowerAccepts addObject:[obj lowercaseString]];
+    }];
 
-    // if `application/json` in acceptArray, return it
-    if ([acceptArray containsObject:[@"application/json" lowercaseString]]) {
+    
+    if ([lowerAccepts containsObject:@"application/json"]) {
         return @"application/json";
     }
     else {
-        return [acceptArray componentsJoinedByString:@", "];
+        return [lowerAccepts componentsJoinedByString:@", "];
     }
 }
 
 /*
- * Detect `Content-Type` from contentTypeArray
+ * Detect `Content-Type` from contentTypes
  */
-+ (NSString *) selectHeaderContentType:(NSArray *)contentTypeArray
++ (NSString *) selectHeaderContentType:(NSArray *)contentTypes
 {
-  // if contentTypeArray is nil or empty, return `application/json`
-  if (contentTypeArray == nil || [contentTypeArray count] == 0) {
-    return @"application/json";
-  }
+    if (contentTypes == nil || [contentTypes count] == 0) {
+        return @"application/json";
+    }
+    
+    NSMutableArray *lowerContentTypes = [[NSMutableArray alloc] initWithCapacity:[contentTypes count]];
+    [contentTypes enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
+        [lowerContentTypes addObject:[obj lowercaseString]];
+    }];
 
-  // if `application/json` in contentTypeArray, return it
-  if ([contentTypeArray containsObject:[@"application/json" lowercaseString]]) {
-    return @"applications/json";
-  }
-  else {
-    return contentTypeArray[0];
-  }
+    if ([lowerContentTypes containsObject:@"application/json"]) {
+        return @"application/json";
+    }
+    else {
+        return lowerContentTypes[0];
+    }
 }
 
 -(void)setHeaderValue:(NSString*) value
diff --git a/modules/swagger-codegen/src/main/resources/objc/api-body.mustache b/modules/swagger-codegen/src/main/resources/objc/api-body.mustache
index 34e20e36f9aa..b18790e3b6f2 100644
--- a/modules/swagger-codegen/src/main/resources/objc/api-body.mustache
+++ b/modules/swagger-codegen/src/main/resources/objc/api-body.mustache
@@ -98,14 +98,22 @@ static NSString * basePath = @"{{basePath}}";
     {{/headerParams}}
     
     // HTTP header `Accept` 
-    NSArray *headerAccept = @[{{#produces}}@"{{mediaType}}"{{#hasMore}}, {{/hasMore}}{{/produces}}];
-    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:headerAccept];
-    NSString *responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:@[{{#produces}}@"{{mediaType}}"{{#hasMore}}, {{/hasMore}}{{/produces}}]];
+    if ([headerParams[@"Accept"] length] == 0) {
+        [headerParams removeObjectForKey:@"Accept"];
+    }
 
-    // HTTP header `Content-Type`
-    NSArray *headerContentType = @[{{#consumes}}@"{{mediaType}}"{{#hasMore}}, {{/hasMore}}{{/consumes}}];
-    headerParams[@"Content-Type"] = [SWGApiClient selectHeaderContentType:headerContentType];
-    NSString *requestContentType = headerParams[@"Content-Type"];
+    // response content type
+    NSString *responseContentType;
+    if ([headerParams objectForKey:@"Accept"]) {
+        responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    }
+    else {
+        responseContentType = @"";
+    }
+
+    // request content type
+    NSString *requestContentType = [SWGApiClient selectHeaderContentType:@[{{#consumes}}@"{{mediaType}}"{{#hasMore}}, {{/hasMore}}{{/consumes}}]];
 
     id bodyDictionary = nil;
     {{#bodyParam}}
diff --git a/samples/client/petstore/objc/PetstoreClient/PetstoreClient.xcodeproj/project.pbxproj b/samples/client/petstore/objc/PetstoreClient/PetstoreClient.xcodeproj/project.pbxproj
index a3f7b4cae6b2..723caec2cdbf 100644
--- a/samples/client/petstore/objc/PetstoreClient/PetstoreClient.xcodeproj/project.pbxproj
+++ b/samples/client/petstore/objc/PetstoreClient/PetstoreClient.xcodeproj/project.pbxproj
@@ -8,6 +8,7 @@
 
 /* Begin PBXBuildFile section */
 		BA525648922D4C0E9F44D4F1 /* libPods.a in Frameworks */ = {isa = PBXBuildFile; fileRef = 73DA4F1067C343C3962F1542 /* libPods.a */; };
+		CF31D0991B105E4B00509935 /* SWGApiClientTest.m in Sources */ = {isa = PBXBuildFile; fileRef = CF31D0981B105E4B00509935 /* SWGApiClientTest.m */; };
 		CFD1B6701B05EC7D00DCCD51 /* JSONValueTransformer+ISO8601.m in Sources */ = {isa = PBXBuildFile; fileRef = CFD1B66F1B05EC7D00DCCD51 /* JSONValueTransformer+ISO8601.m */; };
 		CFD1B6711B05EC7D00DCCD51 /* JSONValueTransformer+ISO8601.m in Sources */ = {isa = PBXBuildFile; fileRef = CFD1B66F1B05EC7D00DCCD51 /* JSONValueTransformer+ISO8601.m */; };
 		EA66999A1811D2FA00A70D03 /* Foundation.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = EA6699991811D2FA00A70D03 /* Foundation.framework */; };
@@ -55,6 +56,7 @@
 /* Begin PBXFileReference section */
 		73DA4F1067C343C3962F1542 /* libPods.a */ = {isa = PBXFileReference; explicitFileType = archive.ar; includeInIndex = 0; path = libPods.a; sourceTree = BUILT_PRODUCTS_DIR; };
 		A425648B5C0A4849C7668069 /* Pods.release.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = Pods.release.xcconfig; path = "../Pods/Target Support Files/Pods/Pods.release.xcconfig"; sourceTree = "<group>"; };
+		CF31D0981B105E4B00509935 /* SWGApiClientTest.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = SWGApiClientTest.m; sourceTree = "<group>"; };
 		CFD1B66E1B05EC7D00DCCD51 /* JSONValueTransformer+ISO8601.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = "JSONValueTransformer+ISO8601.h"; sourceTree = "<group>"; };
 		CFD1B66F1B05EC7D00DCCD51 /* JSONValueTransformer+ISO8601.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = "JSONValueTransformer+ISO8601.m"; sourceTree = "<group>"; };
 		E2B6DA00BE52336E23783686 /* Pods.debug.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = Pods.debug.xcconfig; path = "../Pods/Target Support Files/Pods/Pods.debug.xcconfig"; sourceTree = "<group>"; };
@@ -207,6 +209,7 @@
 			isa = PBXGroup;
 			children = (
 				EA8CD3EB1AC274BE00C47D0B /* PetApiTest.h */,
+				CF31D0981B105E4B00509935 /* SWGApiClientTest.m */,
 				EA6699C71811D2FB00A70D03 /* PetApiTest.m */,
 				EA6699C21811D2FB00A70D03 /* Supporting Files */,
 			);
@@ -417,6 +420,7 @@
 				EAB26B0C1AC8DF78002F5C7A /* PetApiTest.h in Sources */,
 				CFD1B6711B05EC7D00DCCD51 /* JSONValueTransformer+ISO8601.m in Sources */,
 				EAB26B0D1AC8DF78002F5C7A /* PetApiTest.m in Sources */,
+				CF31D0991B105E4B00509935 /* SWGApiClientTest.m in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
diff --git a/samples/client/petstore/objc/PetstoreClient/PetstoreClientTests/SWGApiClientTest.m b/samples/client/petstore/objc/PetstoreClient/PetstoreClientTests/SWGApiClientTest.m
new file mode 100644
index 000000000000..0464bf569e9f
--- /dev/null
+++ b/samples/client/petstore/objc/PetstoreClient/PetstoreClientTests/SWGApiClientTest.m
@@ -0,0 +1,59 @@
+#import <UIKit/UIKit.h>
+#import <XCTest/XCTest.h>
+#import "SWGApiClient.h"
+
+@interface SWGApiClientTest : XCTestCase
+
+@end
+
+@implementation SWGApiClientTest
+
+- (void)setUp {
+    [super setUp];
+    // Put setup code here. This method is called before the invocation of each test method in the class.
+}
+
+- (void)tearDown {
+    // Put teardown code here. This method is called after the invocation of each test method in the class.
+    [super tearDown];
+}
+
+- (void)testSelectHeaderAccept {
+    NSArray *accepts = nil;
+    
+    accepts = @[@"APPLICATION/JSON", @"APPLICATION/XML"];
+    XCTAssertEqualObjects([SWGApiClient selectHeaderAccept:accepts], @"application/json");
+    
+    accepts = @[@"application/json", @"application/xml"];
+    XCTAssertEqualObjects([SWGApiClient selectHeaderAccept:accepts], @"application/json");
+    
+    accepts = @[@"APPLICATION/xml", @"APPLICATION/json"];
+    XCTAssertEqualObjects([SWGApiClient selectHeaderAccept:accepts], @"application/json");
+    
+    accepts = @[@"text/plain", @"application/xml"];
+    XCTAssertEqualObjects([SWGApiClient selectHeaderAccept:accepts], @"text/plain, application/xml");
+    
+    accepts = @[];
+    XCTAssertEqualObjects([SWGApiClient selectHeaderAccept:accepts], @"");
+}
+
+- (void)testSelectHeaderContentType {
+    NSArray *contentTypes = nil;
+    
+    contentTypes = @[@"APPLICATION/JSON", @"APPLICATION/XML"];
+    XCTAssertEqualObjects([SWGApiClient selectHeaderContentType:contentTypes], @"application/json");
+    
+    contentTypes = @[@"application/json", @"application/xml"];
+    XCTAssertEqualObjects([SWGApiClient selectHeaderContentType:contentTypes], @"application/json");
+    
+    contentTypes = @[@"APPLICATION/xml", @"APPLICATION/json"];
+    XCTAssertEqualObjects([SWGApiClient selectHeaderContentType:contentTypes], @"application/json");
+    
+    contentTypes = @[@"text/plain", @"application/xml"];
+    XCTAssertEqualObjects([SWGApiClient selectHeaderContentType:contentTypes], @"text/plain");
+    
+    contentTypes = @[];
+    XCTAssertEqualObjects([SWGApiClient selectHeaderContentType:contentTypes], @"application/json");
+}
+
+@end
diff --git a/samples/client/petstore/objc/Podfile.lock b/samples/client/petstore/objc/Podfile.lock
index fe43a2c80ebf..6ac776ab37a8 100644
--- a/samples/client/petstore/objc/Podfile.lock
+++ b/samples/client/petstore/objc/Podfile.lock
@@ -1,23 +1,23 @@
 PODS:
-  - AFNetworking (2.5.3):
-    - AFNetworking/NSURLConnection (= 2.5.3)
-    - AFNetworking/NSURLSession (= 2.5.3)
-    - AFNetworking/Reachability (= 2.5.3)
-    - AFNetworking/Security (= 2.5.3)
-    - AFNetworking/Serialization (= 2.5.3)
-    - AFNetworking/UIKit (= 2.5.3)
-  - AFNetworking/NSURLConnection (2.5.3):
+  - AFNetworking (2.5.4):
+    - AFNetworking/NSURLConnection (= 2.5.4)
+    - AFNetworking/NSURLSession (= 2.5.4)
+    - AFNetworking/Reachability (= 2.5.4)
+    - AFNetworking/Security (= 2.5.4)
+    - AFNetworking/Serialization (= 2.5.4)
+    - AFNetworking/UIKit (= 2.5.4)
+  - AFNetworking/NSURLConnection (2.5.4):
     - AFNetworking/Reachability
     - AFNetworking/Security
     - AFNetworking/Serialization
-  - AFNetworking/NSURLSession (2.5.3):
+  - AFNetworking/NSURLSession (2.5.4):
     - AFNetworking/Reachability
     - AFNetworking/Security
     - AFNetworking/Serialization
-  - AFNetworking/Reachability (2.5.3)
-  - AFNetworking/Security (2.5.3)
-  - AFNetworking/Serialization (2.5.3)
-  - AFNetworking/UIKit (2.5.3):
+  - AFNetworking/Reachability (2.5.4)
+  - AFNetworking/Security (2.5.4)
+  - AFNetworking/Serialization (2.5.4)
+  - AFNetworking/UIKit (2.5.4):
     - AFNetworking/NSURLConnection
     - AFNetworking/NSURLSession
   - ISO8601 (0.2.0)
@@ -29,8 +29,8 @@ DEPENDENCIES:
   - JSONModel (~> 1.0)
 
 SPEC CHECKSUMS:
-  AFNetworking: e1d86c2a96bb5d2e7408da36149806706ee122fe
+  AFNetworking: 05edc0ac4c4c8cf57bcf4b84be5b0744b6d8e71e
   ISO8601: 962282de75074c38bbfaa7b133b0e743ed6deb8d
   JSONModel: ec77e9865236a7a09d9cf7668df6b4b328d9ec1d
 
-COCOAPODS: 0.36.0
+COCOAPODS: 0.37.1
diff --git a/samples/client/petstore/objc/client/SWGApiClient.m b/samples/client/petstore/objc/client/SWGApiClient.m
index 4547e61277ab..15dbee074594 100644
--- a/samples/client/petstore/objc/client/SWGApiClient.m
+++ b/samples/client/petstore/objc/client/SWGApiClient.m
@@ -80,41 +80,48 @@ static bool loggingEnabled = true;
 }
 
 /*
- * Detect `Accept` from acceptArray
+ * Detect `Accept` from accepts
  */
-+ (NSString *) selectHeaderAccept:(NSArray *)acceptArray
++ (NSString *) selectHeaderAccept:(NSArray *)accepts
 {
-    // if acceptArray is nil or empty, return `application/json`
-    if (acceptArray == nil || [acceptArray count] == 0) {
-        return @"application/json";
+    if (accepts == nil || [accepts count] == 0) {
+        return @"";
     }
+    
+    NSMutableArray *lowerAccepts = [[NSMutableArray alloc] initWithCapacity:[accepts count]];
+    [accepts enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
+        [lowerAccepts addObject:[obj lowercaseString]];
+    }];
 
-    // if `application/json` in acceptArray, return it
-    if ([acceptArray containsObject:[@"application/json" lowercaseString]]) {
+    
+    if ([lowerAccepts containsObject:@"application/json"]) {
         return @"application/json";
     }
     else {
-        return [acceptArray componentsJoinedByString:@", "];
+        return [lowerAccepts componentsJoinedByString:@", "];
     }
 }
 
 /*
- * Detect `Content-Type` from contentTypeArray
+ * Detect `Content-Type` from contentTypes
  */
-+ (NSString *) selectHeaderContentType:(NSArray *)contentTypeArray
++ (NSString *) selectHeaderContentType:(NSArray *)contentTypes
 {
-  // if contentTypeArray is nil or empty, return `application/json`
-  if (contentTypeArray == nil || [contentTypeArray count] == 0) {
-    return @"application/json";
-  }
+    if (contentTypes == nil || [contentTypes count] == 0) {
+        return @"application/json";
+    }
+    
+    NSMutableArray *lowerContentTypes = [[NSMutableArray alloc] initWithCapacity:[contentTypes count]];
+    [contentTypes enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
+        [lowerContentTypes addObject:[obj lowercaseString]];
+    }];
 
-  // if `application/json` in contentTypeArray, return it
-  if ([contentTypeArray containsObject:[@"application/json" lowercaseString]]) {
-    return @"applications/json";
-  }
-  else {
-    return contentTypeArray[0];
-  }
+    if ([lowerContentTypes containsObject:@"application/json"]) {
+        return @"application/json";
+    }
+    else {
+        return lowerContentTypes[0];
+    }
 }
 
 -(void)setHeaderValue:(NSString*) value
diff --git a/samples/client/petstore/objc/client/SWGPetApi.m b/samples/client/petstore/objc/client/SWGPetApi.m
index 2589241dbe4b..9f2b79c51f86 100644
--- a/samples/client/petstore/objc/client/SWGPetApi.m
+++ b/samples/client/petstore/objc/client/SWGPetApi.m
@@ -84,14 +84,22 @@ static NSString * basePath = @"http://petstore.swagger.io/v2";
     
     
     // HTTP header `Accept` 
-    NSArray *headerAccept = @[@"application/json", @"application/xml"];
-    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:headerAccept];
-    NSString *responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:@[@"application/json", @"application/xml"]];
+    if ([headerParams[@"Accept"] length] == 0) {
+        [headerParams removeObjectForKey:@"Accept"];
+    }
 
-    // HTTP header `Content-Type`
-    NSArray *headerContentType = @[@"application/json", @"application/xml", ];
-    headerParams[@"Content-Type"] = [SWGApiClient selectHeaderContentType:headerContentType];
-    NSString *requestContentType = headerParams[@"Content-Type"];
+    // response content type
+    NSString *responseContentType;
+    if ([headerParams objectForKey:@"Accept"]) {
+        responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    }
+    else {
+        responseContentType = @"";
+    }
+
+    // request content type
+    NSString *requestContentType = [SWGApiClient selectHeaderContentType:@[@"application/json", @"application/xml"]];
 
     id bodyDictionary = nil;
     
@@ -174,15 +182,6 @@ static NSString * basePath = @"http://petstore.swagger.io/v2";
 
     
 
-<<<<<<< HEAD
-=======
-    NSArray* requestContentTypes = @[@"application/json", @"application/xml"];
-    NSString* requestContentType = [requestContentTypes count] > 0 ? requestContentTypes[0] : @"application/json";
-
-    NSArray* responseContentTypes = @[@"application/json", @"application/xml"];
-    NSString* responseContentType = [responseContentTypes count] > 0 ? responseContentTypes[0] : @"application/json";
-
->>>>>>> develop_2.0
     NSMutableDictionary* queryParams = [[NSMutableDictionary alloc] init];
     
     NSMutableDictionary* headerParams = [NSMutableDictionary dictionaryWithDictionary:self.defaultHeaders];
@@ -190,14 +189,22 @@ static NSString * basePath = @"http://petstore.swagger.io/v2";
     
     
     // HTTP header `Accept` 
-    NSArray *headerAccept = @[@"application/json", @"application/xml"];
-    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:headerAccept];
-    NSString *responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:@[@"application/json", @"application/xml"]];
+    if ([headerParams[@"Accept"] length] == 0) {
+        [headerParams removeObjectForKey:@"Accept"];
+    }
 
-    // HTTP header `Content-Type`
-    NSArray *headerContentType = @[@"application/json", @"application/xml", ];
-    headerParams[@"Content-Type"] = [SWGApiClient selectHeaderContentType:headerContentType];
-    NSString *requestContentType = headerParams[@"Content-Type"];
+    // response content type
+    NSString *responseContentType;
+    if ([headerParams objectForKey:@"Accept"]) {
+        responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    }
+    else {
+        responseContentType = @"";
+    }
+
+    // request content type
+    NSString *requestContentType = [SWGApiClient selectHeaderContentType:@[@"application/json", @"application/xml"]];
 
     id bodyDictionary = nil;
     
@@ -293,14 +300,22 @@ static NSString * basePath = @"http://petstore.swagger.io/v2";
     
     
     // HTTP header `Accept` 
-    NSArray *headerAccept = @[@"application/json", @"application/xml"];
-    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:headerAccept];
-    NSString *responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:@[@"application/json", @"application/xml"]];
+    if ([headerParams[@"Accept"] length] == 0) {
+        [headerParams removeObjectForKey:@"Accept"];
+    }
 
-    // HTTP header `Content-Type`
-    NSArray *headerContentType = @[];
-    headerParams[@"Content-Type"] = [SWGApiClient selectHeaderContentType:headerContentType];
-    NSString *requestContentType = headerParams[@"Content-Type"];
+    // response content type
+    NSString *responseContentType;
+    if ([headerParams objectForKey:@"Accept"]) {
+        responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    }
+    else {
+        responseContentType = @"";
+    }
+
+    // request content type
+    NSString *requestContentType = [SWGApiClient selectHeaderContentType:@[]];
 
     id bodyDictionary = nil;
     
@@ -386,14 +401,22 @@ static NSString * basePath = @"http://petstore.swagger.io/v2";
     
     
     // HTTP header `Accept` 
-    NSArray *headerAccept = @[@"application/json", @"application/xml"];
-    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:headerAccept];
-    NSString *responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:@[@"application/json", @"application/xml"]];
+    if ([headerParams[@"Accept"] length] == 0) {
+        [headerParams removeObjectForKey:@"Accept"];
+    }
 
-    // HTTP header `Content-Type`
-    NSArray *headerContentType = @[];
-    headerParams[@"Content-Type"] = [SWGApiClient selectHeaderContentType:headerContentType];
-    NSString *requestContentType = headerParams[@"Content-Type"];
+    // response content type
+    NSString *responseContentType;
+    if ([headerParams objectForKey:@"Accept"]) {
+        responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    }
+    else {
+        responseContentType = @"";
+    }
+
+    // request content type
+    NSString *requestContentType = [SWGApiClient selectHeaderContentType:@[]];
 
     id bodyDictionary = nil;
     
@@ -477,22 +500,22 @@ static NSString * basePath = @"http://petstore.swagger.io/v2";
     
     
     // HTTP header `Accept` 
-    NSArray *headerAccept = @[];
-    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:headerAccept];
-    NSString *responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
-
-    // HTTP header `Content-Type`
-    NSArray *headerContentType = @[];
-    headerParams[@"Content-Type"] = [SWGApiClient selectHeaderContentType:headerContentType];
-    NSString *requestContentType = headerParams[@"Content-Type"];
-             
-             NSLog(@"--------------------------------");
-             NSLog(@"request type: %@", requestContentType);
-             NSLog(@"response type: %@", responseContentType);
-             NSLog(@"headers: %@", headerParams);
-             NSLog(@"--------------------------------");
+    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:@[@"application/json", @"application/xml"]];
+    if ([headerParams[@"Accept"] length] == 0) {
+        [headerParams removeObjectForKey:@"Accept"];
+    }
 
+    // response content type
+    NSString *responseContentType;
+    if ([headerParams objectForKey:@"Accept"]) {
+        responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    }
+    else {
+        responseContentType = @"";
+    }
 
+    // request content type
+    NSString *requestContentType = [SWGApiClient selectHeaderContentType:@[]];
 
     id bodyDictionary = nil;
     
@@ -574,15 +597,6 @@ static NSString * basePath = @"http://petstore.swagger.io/v2";
     [requestUrl replaceCharactersInRange: [requestUrl rangeOfString:[NSString stringWithFormat:@"%@%@%@", @"{", @"petId", @"}"]] withString: [SWGApiClient escape:petId]];
     
 
-<<<<<<< HEAD
-=======
-    NSArray* requestContentTypes = @[@"application/x-www-form-urlencoded"];
-    NSString* requestContentType = [requestContentTypes count] > 0 ? requestContentTypes[0] : @"application/json";
-
-    NSArray* responseContentTypes = @[@"application/json", @"application/xml"];
-    NSString* responseContentType = [responseContentTypes count] > 0 ? responseContentTypes[0] : @"application/json";
-
->>>>>>> develop_2.0
     NSMutableDictionary* queryParams = [[NSMutableDictionary alloc] init];
     
     NSMutableDictionary* headerParams = [NSMutableDictionary dictionaryWithDictionary:self.defaultHeaders];
@@ -590,14 +604,22 @@ static NSString * basePath = @"http://petstore.swagger.io/v2";
     
     
     // HTTP header `Accept` 
-    NSArray *headerAccept = @[@"application/json", @"application/xml"];
-    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:headerAccept];
-    NSString *responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:@[@"application/json", @"application/xml"]];
+    if ([headerParams[@"Accept"] length] == 0) {
+        [headerParams removeObjectForKey:@"Accept"];
+    }
 
-    // HTTP header `Content-Type`
-    NSArray *headerContentType = @[@"application/x-www-form-urlencoded", ];
-    headerParams[@"Content-Type"] = [SWGApiClient selectHeaderContentType:headerContentType];
-    NSString *requestContentType = headerParams[@"Content-Type"];
+    // response content type
+    NSString *responseContentType;
+    if ([headerParams objectForKey:@"Accept"]) {
+        responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    }
+    else {
+        responseContentType = @"";
+    }
+
+    // request content type
+    NSString *requestContentType = [SWGApiClient selectHeaderContentType:@[@"application/x-www-form-urlencoded"]];
 
     id bodyDictionary = nil;
     
@@ -688,14 +710,22 @@ static NSString * basePath = @"http://petstore.swagger.io/v2";
     
     
     // HTTP header `Accept` 
-    NSArray *headerAccept = @[@"application/json", @"application/xml"];
-    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:headerAccept];
-    NSString *responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:@[@"application/json", @"application/xml"]];
+    if ([headerParams[@"Accept"] length] == 0) {
+        [headerParams removeObjectForKey:@"Accept"];
+    }
 
-    // HTTP header `Content-Type`
-    NSArray *headerContentType = @[];
-    headerParams[@"Content-Type"] = [SWGApiClient selectHeaderContentType:headerContentType];
-    NSString *requestContentType = headerParams[@"Content-Type"];
+    // response content type
+    NSString *responseContentType;
+    if ([headerParams objectForKey:@"Accept"]) {
+        responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    }
+    else {
+        responseContentType = @"";
+    }
+
+    // request content type
+    NSString *requestContentType = [SWGApiClient selectHeaderContentType:@[]];
 
     id bodyDictionary = nil;
     
@@ -763,15 +793,6 @@ static NSString * basePath = @"http://petstore.swagger.io/v2";
     [requestUrl replaceCharactersInRange: [requestUrl rangeOfString:[NSString stringWithFormat:@"%@%@%@", @"{", @"petId", @"}"]] withString: [SWGApiClient escape:petId]];
     
 
-<<<<<<< HEAD
-=======
-    NSArray* requestContentTypes = @[@"multipart/form-data"];
-    NSString* requestContentType = [requestContentTypes count] > 0 ? requestContentTypes[0] : @"application/json";
-
-    NSArray* responseContentTypes = @[@"application/json", @"application/xml"];
-    NSString* responseContentType = [responseContentTypes count] > 0 ? responseContentTypes[0] : @"application/json";
-
->>>>>>> develop_2.0
     NSMutableDictionary* queryParams = [[NSMutableDictionary alloc] init];
     
     NSMutableDictionary* headerParams = [NSMutableDictionary dictionaryWithDictionary:self.defaultHeaders];
@@ -779,14 +800,22 @@ static NSString * basePath = @"http://petstore.swagger.io/v2";
     
     
     // HTTP header `Accept` 
-    NSArray *headerAccept = @[@"application/json", @"application/xml"];
-    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:headerAccept];
-    NSString *responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:@[@"application/json", @"application/xml"]];
+    if ([headerParams[@"Accept"] length] == 0) {
+        [headerParams removeObjectForKey:@"Accept"];
+    }
 
-    // HTTP header `Content-Type`
-    NSArray *headerContentType = @[@"multipart/form-data", ];
-    headerParams[@"Content-Type"] = [SWGApiClient selectHeaderContentType:headerContentType];
-    NSString *requestContentType = headerParams[@"Content-Type"];
+    // response content type
+    NSString *responseContentType;
+    if ([headerParams objectForKey:@"Accept"]) {
+        responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    }
+    else {
+        responseContentType = @"";
+    }
+
+    // request content type
+    NSString *requestContentType = [SWGApiClient selectHeaderContentType:@[@"multipart/form-data"]];
 
     id bodyDictionary = nil;
     
diff --git a/samples/client/petstore/objc/client/SWGStoreApi.m b/samples/client/petstore/objc/client/SWGStoreApi.m
index e4ac4f4e8c0d..75875ff4eae8 100644
--- a/samples/client/petstore/objc/client/SWGStoreApi.m
+++ b/samples/client/petstore/objc/client/SWGStoreApi.m
@@ -81,14 +81,22 @@ static NSString * basePath = @"http://petstore.swagger.io/v2";
     
     
     // HTTP header `Accept` 
-    NSArray *headerAccept = @[@"application/json", @"application/xml"];
-    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:headerAccept];
-    NSString *responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:@[@"application/json", @"application/xml"]];
+    if ([headerParams[@"Accept"] length] == 0) {
+        [headerParams removeObjectForKey:@"Accept"];
+    }
 
-    // HTTP header `Content-Type`
-    NSArray *headerContentType = @[];
-    headerParams[@"Content-Type"] = [SWGApiClient selectHeaderContentType:headerContentType];
-    NSString *requestContentType = headerParams[@"Content-Type"];
+    // response content type
+    NSString *responseContentType;
+    if ([headerParams objectForKey:@"Accept"]) {
+        responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    }
+    else {
+        responseContentType = @"";
+    }
+
+    // request content type
+    NSString *requestContentType = [SWGApiClient selectHeaderContentType:@[]];
 
     id bodyDictionary = nil;
     
@@ -161,14 +169,22 @@ static NSString * basePath = @"http://petstore.swagger.io/v2";
     
     
     // HTTP header `Accept` 
-    NSArray *headerAccept = @[@"application/json", @"application/xml"];
-    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:headerAccept];
-    NSString *responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:@[@"application/json", @"application/xml"]];
+    if ([headerParams[@"Accept"] length] == 0) {
+        [headerParams removeObjectForKey:@"Accept"];
+    }
 
-    // HTTP header `Content-Type`
-    NSArray *headerContentType = @[];
-    headerParams[@"Content-Type"] = [SWGApiClient selectHeaderContentType:headerContentType];
-    NSString *requestContentType = headerParams[@"Content-Type"];
+    // response content type
+    NSString *responseContentType;
+    if ([headerParams objectForKey:@"Accept"]) {
+        responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    }
+    else {
+        responseContentType = @"";
+    }
+
+    // request content type
+    NSString *requestContentType = [SWGApiClient selectHeaderContentType:@[]];
 
     id bodyDictionary = nil;
     
@@ -276,14 +292,22 @@ static NSString * basePath = @"http://petstore.swagger.io/v2";
     
     
     // HTTP header `Accept` 
-    NSArray *headerAccept = @[@"application/json", @"application/xml"];
-    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:headerAccept];
-    NSString *responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:@[@"application/json", @"application/xml"]];
+    if ([headerParams[@"Accept"] length] == 0) {
+        [headerParams removeObjectForKey:@"Accept"];
+    }
 
-    // HTTP header `Content-Type`
-    NSArray *headerContentType = @[];
-    headerParams[@"Content-Type"] = [SWGApiClient selectHeaderContentType:headerContentType];
-    NSString *requestContentType = headerParams[@"Content-Type"];
+    // response content type
+    NSString *responseContentType;
+    if ([headerParams objectForKey:@"Accept"]) {
+        responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    }
+    else {
+        responseContentType = @"";
+    }
+
+    // request content type
+    NSString *requestContentType = [SWGApiClient selectHeaderContentType:@[]];
 
     id bodyDictionary = nil;
     
@@ -368,14 +392,22 @@ static NSString * basePath = @"http://petstore.swagger.io/v2";
     
     
     // HTTP header `Accept` 
-    NSArray *headerAccept = @[@"application/json", @"application/xml"];
-    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:headerAccept];
-    NSString *responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:@[@"application/json", @"application/xml"]];
+    if ([headerParams[@"Accept"] length] == 0) {
+        [headerParams removeObjectForKey:@"Accept"];
+    }
 
-    // HTTP header `Content-Type`
-    NSArray *headerContentType = @[];
-    headerParams[@"Content-Type"] = [SWGApiClient selectHeaderContentType:headerContentType];
-    NSString *requestContentType = headerParams[@"Content-Type"];
+    // response content type
+    NSString *responseContentType;
+    if ([headerParams objectForKey:@"Accept"]) {
+        responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    }
+    else {
+        responseContentType = @"";
+    }
+
+    // request content type
+    NSString *requestContentType = [SWGApiClient selectHeaderContentType:@[]];
 
     id bodyDictionary = nil;
     
diff --git a/samples/client/petstore/objc/client/SWGUserApi.m b/samples/client/petstore/objc/client/SWGUserApi.m
index 30af7788af73..3e87268a4c62 100644
--- a/samples/client/petstore/objc/client/SWGUserApi.m
+++ b/samples/client/petstore/objc/client/SWGUserApi.m
@@ -83,14 +83,22 @@ static NSString * basePath = @"http://petstore.swagger.io/v2";
     
     
     // HTTP header `Accept` 
-    NSArray *headerAccept = @[@"application/json", @"application/xml"];
-    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:headerAccept];
-    NSString *responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:@[@"application/json", @"application/xml"]];
+    if ([headerParams[@"Accept"] length] == 0) {
+        [headerParams removeObjectForKey:@"Accept"];
+    }
 
-    // HTTP header `Content-Type`
-    NSArray *headerContentType = @[];
-    headerParams[@"Content-Type"] = [SWGApiClient selectHeaderContentType:headerContentType];
-    NSString *requestContentType = headerParams[@"Content-Type"];
+    // response content type
+    NSString *responseContentType;
+    if ([headerParams objectForKey:@"Accept"]) {
+        responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    }
+    else {
+        responseContentType = @"";
+    }
+
+    // request content type
+    NSString *requestContentType = [SWGApiClient selectHeaderContentType:@[]];
 
     id bodyDictionary = nil;
     
@@ -180,14 +188,22 @@ static NSString * basePath = @"http://petstore.swagger.io/v2";
     
     
     // HTTP header `Accept` 
-    NSArray *headerAccept = @[@"application/json", @"application/xml"];
-    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:headerAccept];
-    NSString *responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:@[@"application/json", @"application/xml"]];
+    if ([headerParams[@"Accept"] length] == 0) {
+        [headerParams removeObjectForKey:@"Accept"];
+    }
 
-    // HTTP header `Content-Type`
-    NSArray *headerContentType = @[];
-    headerParams[@"Content-Type"] = [SWGApiClient selectHeaderContentType:headerContentType];
-    NSString *requestContentType = headerParams[@"Content-Type"];
+    // response content type
+    NSString *responseContentType;
+    if ([headerParams objectForKey:@"Accept"]) {
+        responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    }
+    else {
+        responseContentType = @"";
+    }
+
+    // request content type
+    NSString *requestContentType = [SWGApiClient selectHeaderContentType:@[]];
 
     id bodyDictionary = nil;
     
@@ -277,14 +293,22 @@ static NSString * basePath = @"http://petstore.swagger.io/v2";
     
     
     // HTTP header `Accept` 
-    NSArray *headerAccept = @[@"application/json", @"application/xml"];
-    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:headerAccept];
-    NSString *responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:@[@"application/json", @"application/xml"]];
+    if ([headerParams[@"Accept"] length] == 0) {
+        [headerParams removeObjectForKey:@"Accept"];
+    }
 
-    // HTTP header `Content-Type`
-    NSArray *headerContentType = @[];
-    headerParams[@"Content-Type"] = [SWGApiClient selectHeaderContentType:headerContentType];
-    NSString *requestContentType = headerParams[@"Content-Type"];
+    // response content type
+    NSString *responseContentType;
+    if ([headerParams objectForKey:@"Accept"]) {
+        responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    }
+    else {
+        responseContentType = @"";
+    }
+
+    // request content type
+    NSString *requestContentType = [SWGApiClient selectHeaderContentType:@[]];
 
     id bodyDictionary = nil;
     
@@ -384,14 +408,22 @@ static NSString * basePath = @"http://petstore.swagger.io/v2";
     
     
     // HTTP header `Accept` 
-    NSArray *headerAccept = @[@"application/json", @"application/xml"];
-    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:headerAccept];
-    NSString *responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:@[@"application/json", @"application/xml"]];
+    if ([headerParams[@"Accept"] length] == 0) {
+        [headerParams removeObjectForKey:@"Accept"];
+    }
 
-    // HTTP header `Content-Type`
-    NSArray *headerContentType = @[];
-    headerParams[@"Content-Type"] = [SWGApiClient selectHeaderContentType:headerContentType];
-    NSString *requestContentType = headerParams[@"Content-Type"];
+    // response content type
+    NSString *responseContentType;
+    if ([headerParams objectForKey:@"Accept"]) {
+        responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    }
+    else {
+        responseContentType = @"";
+    }
+
+    // request content type
+    NSString *requestContentType = [SWGApiClient selectHeaderContentType:@[]];
 
     id bodyDictionary = nil;
     
@@ -468,14 +500,22 @@ static NSString * basePath = @"http://petstore.swagger.io/v2";
     
     
     // HTTP header `Accept` 
-    NSArray *headerAccept = @[@"application/json", @"application/xml"];
-    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:headerAccept];
-    NSString *responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:@[@"application/json", @"application/xml"]];
+    if ([headerParams[@"Accept"] length] == 0) {
+        [headerParams removeObjectForKey:@"Accept"];
+    }
 
-    // HTTP header `Content-Type`
-    NSArray *headerContentType = @[];
-    headerParams[@"Content-Type"] = [SWGApiClient selectHeaderContentType:headerContentType];
-    NSString *requestContentType = headerParams[@"Content-Type"];
+    // response content type
+    NSString *responseContentType;
+    if ([headerParams objectForKey:@"Accept"]) {
+        responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    }
+    else {
+        responseContentType = @"";
+    }
+
+    // request content type
+    NSString *requestContentType = [SWGApiClient selectHeaderContentType:@[]];
 
     id bodyDictionary = nil;
     
@@ -546,14 +586,22 @@ static NSString * basePath = @"http://petstore.swagger.io/v2";
     
     
     // HTTP header `Accept` 
-    NSArray *headerAccept = @[@"application/json", @"application/xml"];
-    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:headerAccept];
-    NSString *responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:@[@"application/json", @"application/xml"]];
+    if ([headerParams[@"Accept"] length] == 0) {
+        [headerParams removeObjectForKey:@"Accept"];
+    }
 
-    // HTTP header `Content-Type`
-    NSArray *headerContentType = @[];
-    headerParams[@"Content-Type"] = [SWGApiClient selectHeaderContentType:headerContentType];
-    NSString *requestContentType = headerParams[@"Content-Type"];
+    // response content type
+    NSString *responseContentType;
+    if ([headerParams objectForKey:@"Accept"]) {
+        responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    }
+    else {
+        responseContentType = @"";
+    }
+
+    // request content type
+    NSString *requestContentType = [SWGApiClient selectHeaderContentType:@[]];
 
     id bodyDictionary = nil;
     
@@ -640,14 +688,22 @@ static NSString * basePath = @"http://petstore.swagger.io/v2";
     
     
     // HTTP header `Accept` 
-    NSArray *headerAccept = @[@"application/json", @"application/xml"];
-    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:headerAccept];
-    NSString *responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:@[@"application/json", @"application/xml"]];
+    if ([headerParams[@"Accept"] length] == 0) {
+        [headerParams removeObjectForKey:@"Accept"];
+    }
 
-    // HTTP header `Content-Type`
-    NSArray *headerContentType = @[];
-    headerParams[@"Content-Type"] = [SWGApiClient selectHeaderContentType:headerContentType];
-    NSString *requestContentType = headerParams[@"Content-Type"];
+    // response content type
+    NSString *responseContentType;
+    if ([headerParams objectForKey:@"Accept"]) {
+        responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    }
+    else {
+        responseContentType = @"";
+    }
+
+    // request content type
+    NSString *requestContentType = [SWGApiClient selectHeaderContentType:@[]];
 
     id bodyDictionary = nil;
     
@@ -741,14 +797,22 @@ static NSString * basePath = @"http://petstore.swagger.io/v2";
     
     
     // HTTP header `Accept` 
-    NSArray *headerAccept = @[@"application/json", @"application/xml"];
-    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:headerAccept];
-    NSString *responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    headerParams[@"Accept"] = [SWGApiClient selectHeaderAccept:@[@"application/json", @"application/xml"]];
+    if ([headerParams[@"Accept"] length] == 0) {
+        [headerParams removeObjectForKey:@"Accept"];
+    }
 
-    // HTTP header `Content-Type`
-    NSArray *headerContentType = @[];
-    headerParams[@"Content-Type"] = [SWGApiClient selectHeaderContentType:headerContentType];
-    NSString *requestContentType = headerParams[@"Content-Type"];
+    // response content type
+    NSString *responseContentType;
+    if ([headerParams objectForKey:@"Accept"]) {
+        responseContentType = [headerParams[@"Accept"] componentsSeparatedByString:@", "][0];
+    }
+    else {
+        responseContentType = @"";
+    }
+
+    // request content type
+    NSString *requestContentType = [SWGApiClient selectHeaderContentType:@[]];
 
     id bodyDictionary = nil;