title: How to get a button's frame in the controller's root view
body: <p>In my view controller, I add a container view as the root view's subview. After that I create a button as the container's subview. I want to get the button's frame in the root view. But when I use <code>button.frame</code> I got the button's frame related to the container. So, can some one tell me how to get the right frame of the button relate to the controller's root view?</p>
  
  <p>Thanks, waiting for your help.</p>