title: iOS - When a UIView appears on screen what method does it call?
body: <p>When a UIView appears on screen what method does it call? 
  For example if a have a UIScrollView and I populate it with a hundred views, one under the other,
  what method is called by the UIViews when they are scrolled such that they appear on screen?</p>
  
  <p>is it -(void)didMoveToWindow  ? something else ?</p>