title: AFNetworking 2.0 - use responseObject as NSDictionary
body: <pre><code>AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];
  [manager GET:@"http://example.com/resources.json" parameters:nil success:^(AFHTTPRequestOperation *operation, id responseObject) {
      NSLog(@"JSON: %@", responseObject);
  } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
      NSLog(@"Error: %@", error);
  }];
  </code></pre>
  
  <p>this is the <a href="https://github.com/AFNetworking/AFNetworking#get-request" rel="noreferrer">recommended way</a> to send <code>GET</code> request in AFNetworking 2.0. I want to get the value of a specific key in the json, so I want to use <code>responseObject</code> as <code>NSDictionary</code>. this is what I was trying:</p>
  
  <pre><code>NSError *jsonError = nil;
  NSDictionary *json = [NSJSONSerialization JSONObjectWithData:(NSData *)responseObject options:kNilOptions error:&amp;jsonError];
  </code></pre>
  
  <p>it didn't work: </p>
  
  <pre><code> *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFDictionary bytes]: unrecognized selector sent to instance 0xa048120'
  </code></pre>
  
  <p>how can I get the value of a specific key in <code>responseObject</code>?</p>