title: Prevent UIScrollView's UIPanGestureRecognizer from blocking UIScreenEdgePanGestureRecognizer
body: <p>I have a <code>UIScrollView</code> that fills the screen on one page of my app, but I want to allow the user to pan from the edge of the screen to reveal a view behind it. The problem is that the UIScrollView steals the touches from my <code>UIScreenEdgePanGestureRecognizer</code> at the edge of the screen. Unfortunately, I can't access the <code>UIScreenEdgePanGestureRecognizer</code> from the view controller that has the <code>UIScrollView</code> (and vice-versa), so I am not able to use the method <code>requireGestureRecognizerToFail:</code> because I cannot able to specify which gesture recognizer should be allowed to fail. The view controller with the scroll view is a child view controller of a container view controller that has the screen edge pan gesture recognizer attached to one of the container view controller's own views.</p>
  
  <p>I'm also unable to use the delegate method</p>
  
  <pre><code>-(BOOL)gestureRecognizer:shouldRequireFailureOfGestureRecognizer:
  </code></pre>
  
  <p>because the <code>UIScrollView</code> won't allow me to set my view controller as the delegate of the scroll view's <code>UIPanGestureRecognizer</code>. </p>
  
  <p>How can I prevent the scrollview from stealing the edge pan touches from my own gesture recognizer?</p>