Stuck with AFNetworking - ios

Question

Am unable to find the real problem with my code. Am using the same code for all other APIs and everything working fine but one API is giving problem.
NSString *strUrl = [[NSString stringWithFormat:#"%#%#",baseURL,apiURL] stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:strUrl] cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:30.0];
//request type may be "POST" or "GET"
[request setHTTPMethod:requestType];
[request setValue:secretKey forHTTPHeaderField:key];
//contentType may be "application/json" or "text/html"
[request setValue:contentType forHTTPHeaderField:#"Accept"];
[request setValue:contentType forHTTPHeaderField:#"Content-Type"];
AFHTTPRequestOperation *requestOperation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
requestOperation.responseSerializer = [AFJSONResponseSerializer serializer];
[requestOperation setShouldExecuteAsBackgroundTaskWithExpirationHandler:^{
completion(nil);
}];
[requestOperation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation * _Nonnull operation, id _Nonnull responseObject) {
completion(nil);
} failure:^(AFHTTPRequestOperation * _Nonnull operation, NSError * _Nonnull error) {
completion(nil);
}];
This code is working for all APIs except one. It's giving me this error in error block.
Error Domain=com.alamofire.error.serialization.response Code=-1016 "Request failed: unacceptable content-type: text/html"
I have then tried to add the acceptable content type by doing this.
requestOperation.responseSerializer.acceptableContentTypes = [requestOperation.responseSerializer.acceptableContentTypes setByAddingObject:#"text/html"];
This did not work. Then i changed the response serializer to AFHTTPResponseSerializer and removed the acceptable content types line. Then the response came as NSData and I parsed the NSData response to JSON object for all other APIs. But this API is giving this error after changing the response serializer. Here is the error from error block.
JSON text did not start with array or object and option to allow fragments not set.
Am not getting this why this happening. I have tried to change the header acceptable content type to json and html. But those are not making any difference. I have tried the API in Chrome Postman and it's working absolutely fine. Please suggest something, where am doing wrong.

Answer 1

Set Content-type to application/Json and try
[request setValue:#"application/json" forHTTPHeaderField:#"Content-Type"];