title: ios: disable forward touch event
body: <p>The view tree in my program like this:</p>
  
  <pre>
  rootView
    --- subView
  </pre>
  
  <p>my problem is how to disable forward touch event from rootView to subView.like:</p>
  
  <pre><code>if(shouldForward){
       [rootView passTouchEventToSubView];
  }
  else{
     //do nothing
  }
  </code></pre>