AFNetworking post parameters not encoding - ios

Question

I'm getting an error using AFNetworking 2.0 while using post method in Swift language because the body isn't encoded as it should be, here is my code:
let manager = AFHTTPRequestOperationManager()
manager.securityPolicy.allowInvalidCertificates = true;
let reqSerializer: AFJSONRequestSerializer = AFJSONRequestSerializer()
reqSerializer.setValue("T-Rex", forHTTPHeaderField: "User-Agent")
reqSerializer.setValue("no-cache", forHTTPHeaderField: "Cache-Control")
reqSerializer.setValue("apikey", forHTTPHeaderField: "Authorization")
manager.requestSerializer = reqSerializer
let resSerializer: AFJSONResponseSerializer = AFJSONResponseSerializer()
resSerializer.acceptableContentTypes = ["text/html", "application/json"]
manager.responseSerializer = resSerializer;
let params: NSDictionary = ["userName" : userName, "passWord" : passWord]
manager.POST(Constants.apiURL.url + "users/login",
parameters:params,
success: { (operation: AFHTTPRequestOperation!, responseObject: AnyObject!) in
NSLog("Success! Response is \(responseObject.description)")
},
failure: { (operation: AFHTTPRequestOperation!, error: NSError!) in
NSLog("Failure! Error is: \(error.localizedDescription)")
})
Debugging the request I get:
POST 'http://api.cc/users/login': {
Accept = "application/json";
"Accept-Language" = "pt;q=1, fr;q=0.9, en;q=0.8";
Authorization = apikey;
"Cache-Control" = "no-cache";
"Content-Type" = "application/json";
"User-Agent" = "T-Rex";
} {"passWord":"123","userName":"123"}
and my server answer:
400 'http://api.cc/users/login' [0.7545 s]: {
Age = 0;
Connection = "keep-alive";
"Content-Length" = 83;
"Content-Type" = "application/json";
Date = "Sun, 06 Sep 2015 01:03:00 GMT";
Server = "nginx/1.8.0";
Via = "1.1 varnish-v4";
"X-Varnish" = 950329;
} {"error":true,"message":"Required field(s) userName, passWord is missing or empty"}
I don't know why the username and password is encoded like this:
{"passWord":"123","userName":"123"}
instead of this:
{"passWord:123&userName":123"}

Answer 1

Should AFHTTPRequestSerializer instead of AFJSONRequestSerializer.
Problem solved.