title: UIPageViewController: return the current visible view
body: <p>How do you know what is the current page/view displayed inside an <code>UIPageViewController</code>?</p>
  
  <p>I have overridden the <code>viewDidAppear</code> method of my child views, so that they send an id to the parent view in their <code>viewDidAppear</code> method.</p>
  
  <p>However, the problem is this: i cannot reliably use that id as id for the displayed page. because if the user turns the page but halfway through decides to stop the turning and put the page back, <code>viewDidAppear</code> will already have been called. (the view is visible behind the curled page).</p>
  
  <p>Maybe i should only switch to a new id if the current view disappears. But I wonder if there is not a more simple way to return the view that is currently visible? </p>