title: UITabViewController includes UINavigationController
body: <p>I have an app which is a UITabViewController in root, include 2 UIViewControllers and 1 UIavigationController. The UINavigationController includes another UIViewController (the third).</p>
  
  <p>The app works well on iPhone.</p>
  
  <p>When I migrate it to iPad, when I set the breakpoint on viewDidLoad of the third UIViewController, I found that it was not being triggered.</p>
  
  <p>Welcome any comment</p>