title: push viewcontroller using UINavigationController sometimes calls viewDidAppear: and viewWillAppear:
body: <p>When pushing a viewcontroller using UINavigationController into the view:</p>
  
  <ol>
  <li>What is necessary for it to trigger
  viewDidAppear: and viewWillAppear: ?</li>
  <li>What makes it fail to not trigger viewDidAppear: and viewWillAppear: ?</li>
  </ol>
  
  <p>We are having a hard time relying on wether those methods gets triggered or not. </p>