Correct way to use AFHTTPSessionManager as a singleton?

Question

I'm trying to use AFNetworking 2.0 to perform my network requests but I'm running into some odd behavior. I've subclassed AFHTTPSessionManager as suggested in the documentation and provided a class method that returns a singleton object that has the base url set as well as sets my auth header.

+ (id)sharedInstance {
  static dispatch_once_t once;
  static MyHTTPClient *sharedInstance;

  dispatch_once(&once, ^{
    sharedInstance = [[self alloc] initWithBaseURL: NSURLURLWithString:kPlatformAPIBaseURL]];
  });

  //Uncommenting this line makes the error go away
  //sharedInstance.responseSerializer = [AFJSONResponseSerializer serializer];

  //get latest session id everytime someone gets an instance of the client
  sharedInstance.sessionId = [MySessionManager getSessionId];

  return sharedInstance;
}

- (instancetype)initWithBaseURL:(NSURL *)url {
  self = [super initWithBaseURL:url];

  if(self) {
    self.sessionId = [FSSessionManager getSessionId];

    self.serializer = [AFHTTPRequestSerializer serializer];
    [_serializer setValue:_sessionId forHTTPHeaderField:kAuthorizationHeader];
    [_serializer setValue:@"application/json" forHTTPHeaderField:kAcceptHeader];

    self.requestSerializer = _serializer;
  }

  return self;
}

- (void)setSessionId:(NSString *)sessionId {
  _sessionId = sessionId;
  [self.serializer setValue:_sessionId forHTTPHeaderField:kAuthorizationHeader];
}

My app uses this to make a POST request to authenticate my user. That works great. I then make a GET request to retrieve a list of objects. Also works great. I then make the same GET request and I get back a network error Error Domain=AFNetworkingErrorDomain Code=-1016 "Request failed: unacceptable content-type: application/json" It's the exact same GET request but it fails on the second call. When I uncomment the sharedInstance.responseSerializer line so I create a new instance of the response serializer each time I get a reference to my shared instance then I don't get this error anymore.

Can a responseSerializer not be used multiple times safely? It feels like some sort of state is hanging around across requests. What's the correct way to set this up?

Answer 1

A response serializer can be used multiple times safely. Based on the error message you posted, "unacceptable content-type: application/json ", it appears you're setting responseSerializer to something else elsewhere in your code. JSON will serialize properly as long as it's set to [AFJSONResponseSerializer serializer].