title: Can't send parameters in POST request in AFNetworking
body: <p>I have playing with AFNetworking. In their example here: <a href="http://cocoadocs.org/docsets/AFNetworking/2.5.0/" rel="nofollow">http://cocoadocs.org/docsets/AFNetworking/2.5.0/</a> there is</p>
  
  <p><code>NSDictionary *parameters = @{@"foo": @"bar"};</code></p>
  
  <p>When i print this variable to console, it shows as </p>
  
  <pre><code>{
      foo = bar;
  }
  </code></pre>
  
  <p>and everything works fine. If i pass to this method my NSMutableDictionary, which contains</p>
  
  <pre><code>{
      apikey = 123;
      stationId = 6;
  }
  </code></pre>
  
  <p>I get this exception: <code>Error Domain=NSCocoaErrorDomain Code=3840 "The operation couldn’t be completed. (Cocoa error 3840.)" (JSON text did not start with array or object and option to allow fragments not set.) UserInfo=0x7bf54c60 {NSDebugDescription=JSON text did not start with array or object and option to allow fragments not set.}</code></p>
  
  <p>I really dont know where is the problem. (I am beginner in Objective C and AFNetworking, so sorry about my unknowledgement :))</p>
  
  <p>Here is full code:</p>
  
  <pre><code>- (void) POST:(NSString *) url withData:(NSMutableDictionary *) jsonData
  {
  AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];
  
  NSString *fullUrl = [self.baseUrl stringByAppendingString:url];
  
  [jsonData setValue:self.apiKey forKey:@"apikey"];
  
  NSLog(@"%@", [jsonData description]);
  NSDictionary *parameters = @{@"stationId": @"6", @"apikey" : @"fdfd"};
  NSLog(@"%@", [parameters description]);
  
  [manager POST:fullUrl parameters:parameters success:^(AFHTTPRequestOperation *operation, id responseObject) {
      NSLog(@"JSON: %@", responseObject);
  } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
      NSLog(@"Error: %@", error);
  }];
  }
  </code></pre>
  
  <p>Thanks for any advice</p>