title: When using a UINavigationController the viewWillAppear or viewDidAppear methods of my controller are not called
body: <p>Here is the pitch.</p>
  
  <ul>
  <li>I have a UIViewController subclass which does something in its viewWillAppear and viewDidAppear methods.</li>
  <li>I want to nest this view controller in a UINavigationViewController.</li>
  <li>Depending on the view hierarchy complexity the two methods <code>viewWillAppear</code> and <code>viewDidAppear</code> of my controller may not be called.</li>
  </ul>
  
  <p>What should I do then to make sure these two methods are always called regardless of my view hierarchy?</p>
  
  <p>Example of a "complex" view hierarchy: </p>
  
  <pre><code>UIViewController subclass containing a UITabBarController
       |_ Each tab containing a UINavigationViewController
           |_ Each UINavigationController controller containing a custom UIViewController
  </code></pre>
  
  <p>When you present the TabBarController as a modal view the <code>viewWillAppear</code> and <code>viewDidAppear</code> methods of the TabBarController are called but not those of the custom UIViewControllers nested under the UINavigationViewControllers.</p>