title: UINavigationController back button press and viewWillDisappear
body: <p>I've got a chat app and I simply want to let the connection manager to leave the current chatroom when the back button on my <code>UINavigationController</code> is pressed (or the view is left in any other way).
  <code>viewWillDisappear:</code> isn't working for me.  </p>
  
  <p>Unlike some others with issues ( <a href="https://stackoverflow.com/questions/4072192/uinavigationcontroller-and-viewwilldisappear">UINavigationController and viewWillDisappear</a> for instance) I have what should be a totally textbook view setup - one <code>UINavigationController</code>, leading into a bunch of subclassed <code>UIViewControllers</code> connected by segues.  What can I do to detect when I leave the chatroom view controller?</p>