title: unrecognized selector sent to instance of UINavigationController
body: <p>I have the main view controller and when the <code>viewDidLoad</code> the user is validated on login via Parse and Facebook:</p>
  
  <pre><code>if ([PFUser currentUser] == nil &amp;&amp; [FBSDKAccessToken currentAccessToken] == nil) {
  
      WelcomeViewController *welcomeController = [self.storyboard instantiateViewControllerWithIdentifier:@"Welcome"];
      [self presentViewController:welcomeController animated:YES completion:nil];
  
  }
  </code></pre>
  
  <p>When I try to push data from the welcome view controller I use <code>self.presentingViewController</code>:</p>
  
  <pre><code>MainFeedTableViewController *mc = (MainFeedTableViewController *)self.presentingViewController;
  mc.username = self.fbUsername;
  </code></pre>
  
  <p><strong>BUT</strong> </p>
  
  <p>the compiler sees it as <code>UINavigationController</code>:</p>
  
  <p><code>-[UINavigationController setUsername:]: unrecognized selector sent to instance 0x7f92b9009a00</code>. </p>
  
  <p>How is that possible when I am presenting with <code>self</code> of the <code>MainFeedTableViewController</code>?</p>