title: [__NSArrayM objectForKeyedSubscript:]: unrecognized selector sent to instance - source code and screenshot attached
body: <p>At GitHub I have <a href="https://github.com/afarber/ios-newbie/tree/master/oauthMailru" rel="noreferrer">a simple iPhone app</a>, which fetches user information (by using OAuth) from the social network Mail.ru:</p>
  
  <p><img src="https://i.stack.imgur.com/TitVb.png" alt="app screenshot"></p>
  
  <p>It does fetch and print the information, but then crashes.</p>
  
  <p>As an iOS programming newbie I'm confused by the output below (also please see <a href="http://pastebin.com/euEjyf3g" rel="noreferrer">the full output at PasteBin</a>):</p>
  
  <pre><code>2014-01-21 21:21:10.873 oauthMailru[8228:3307] -[__NSArrayM objectForKeyedSubscript:]: unrecognized selector sent to instance 0x8a97290
  2014-01-21 21:21:10.875 oauthMailru[8228:3307] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSArrayM objectForKeyedSubscript:]: unrecognized selector sent to instance 0x8a97290'
  *** First throw call stack:
  (
      0   CoreFoundation                      0x01aa65e4 __exceptionPreprocess + 180
      1   libobjc.A.dylib                     0x018298b6 objc_exception_throw + 44
      2   CoreFoundation                      0x01b43903 -[NSObject(NSObject) doesNotRecognizeSelector:] + 275
      3   CoreFoundation                      0x01a9690b ___forwarding___ + 1019
      4   CoreFoundation                      0x01a964ee _CF_forwarding_prep_0 + 14
      5   oauthMailru                         0x00003a62 __47-[ViewController fetchMailruWithToken:ForUser:]_block_invoke + 402
      6   Foundation                          0x01545695 __67+[NSURLConnection sendAsynchronousRequest:queue:completionHandler:]_block_invoke_2 + 151
      7   Foundation                          0x014a5945 -[NSBlockOperation main] + 88
      8   Foundation                          0x014fe829 -[__NSOperationInternal _start:] + 671
      9   Foundation                          0x0147b558 -[NSOperation start] + 83
      10  Foundation                          0x01500af4 __NSOQSchedule_f + 62
      11  libdispatch.dylib                   0x021344b0 _dispatch_client_callout + 14
      12  libdispatch.dylib                   0x02121018 _dispatch_async_redirect_invoke + 202
      13  libdispatch.dylib                   0x021344b0 _dispatch_client_callout + 14
      14  libdispatch.dylib                   0x02122eeb _dispatch_root_queue_drain + 287
      15  libdispatch.dylib                   0x02123137 _dispatch_worker_thread2 + 39
      16  libsystem_pthread.dylib             0x024c0dab _pthread_wqthread + 336
      17  libsystem_pthread.dylib             0x024c4cce start_wqthread + 30
  )
  libc++abi.dylib: terminating with uncaught exception of type NSException
  </code></pre>
  
  <p>Does anybody please know what's happening and how to read such crashes?</p>
  
  <p>My source files: <a href="https://github.com/afarber/ios-newbie/blob/9c6e64af454dbc43a6b5a04e06d3effae93571d1/oauthMailru/oauthMailru/ViewController.m" rel="noreferrer">ViewController.m</a>, which displays <code>UIWebView</code> and then segues to <a href="https://github.com/afarber/ios-newbie/blob/master/oauthMailru/oauthMailru/DetailViewController.m" rel="noreferrer">DetailViewController.m</a></p>