title: How can I know when a `UIViewController` has been just pushed from a `UINavigationViewController`?
body: <p>How can I know when a <code>UIViewController</code> has been just pushed from a <code>UINavigationViewController</code> ?</p>
  
  <p>I obviously don't want to use <code>viewDidAppear</code> because that's method is called everytime that view appears, not just when it's pushed.</p>
  
  <p><code>viewDidLoad</code> is called <em>before</em> the view controller is pushed and I don't have the reference to the navigationController available</p>