title: Navigation from block return
body: <p>I have what I think is a <a href="http://en.wikipedia.org/wiki/User_experience" rel="nofollow">UX</a> operation happening on a background thread. In a method that uses blocks, in the success I am calling:</p>
  
  <pre><code>[self.navigationController popViewControllerAnimated:TRUE]; 
  </code></pre>
  
  <p>I am getting a crash, so I am thinking that checking the current thread and calling performSelectorOnMainThread might fix this, but I am not sure how to setup the @selector portion of the call.</p>
  
  <pre><code>[self performSelectorOnMainThread:@selector([self.navigationController popViewControllerAnimated:TRUE]) withObject:nil waitUntilDone:NO];
  </code></pre>
  
  <p>is not working. What is the proper syntax?</p>