title: iOS 7 use custom interactive transitions only some of the time
body: <p>So I have a UINavigationController, with Controller A as the root controller.</p>
  
  <p>When I want to push Controller B on top, I want to use a custom animated transition and a custom interactive transition. This works fine.</p>
  
  <p>When I want to push Controller C on top, I want to fall back to the <strong><em>default</em></strong> push/pop transitions that comes with UINavigationController. To make this happen I return nil for </p>
  
  <pre><code>navigationController:animationControllerForOperation:fromViewController:toViewController:
  </code></pre>
  
  <p>however if you return nil, then </p>
  
  <pre><code>navigationController:interactionControllerForAnimationController:
  </code></pre>
  
  <p>will never be called and the default "pan from left edge" pop interactive transition doesn't work.</p>
  
  <p>Is there a way to return the default push/pop animation controller and interaction controller? 
  (Are there concrete implementations of <code>id&lt;UIViewControllerAnimatedTransitioning&gt;</code> and <code>id&lt;UIViewControllerInteractiveTransitioning&gt;</code>?)</p>
  
  <p>Or some other way?</p>