title: iOS: different addSubview behavior between iOS 4.3 and 5.0
body: <p>while coding in iOS 4.3 before, I found while add a view controller's view to another view with <code>[superview addSubView:controller.view]</code>, the controller instance will not receive the <code>-viewWillAppear/viewDidAppear</code> message, than I found same issue in some thread in stack overflow. After that, I manually call <code>-viewWillAppear/-viewDidAppear</code> as needed. </p>
  
  <p>but, after upgrade to <code>iOS 5.0</code>, some frisky <code>UIView</code> behavior happened. Finally I found that in iOS 5, the  <code>[superview addSubView:controller.view]</code> , will send a <code>-viewWillAppear/-viewDidAppear</code> message to the controller instance automatically, plus my manually calls, there are two duplicated message each time the controller action its behavior.</p>
  
  <p>and I also found a similar issue: <a href="https://stackoverflow.com/questions/7802673/ios-5-viewwillappear-is-not-called-after-dismissing-the-modal-in-ipad">iOS 5 : -viewWillAppear is not called after dismissing the modal in iPad</a></p>
  
  <p>Now, the problem is, after search apple's documents, I didn't find any explicitly doc for diff about these issues.  I even wonder if this is a guaranteed view life cycle behavior in iOS 5.0 . </p>
  
  <p>Does anyone fix similar issues or find some guidelines about these difference. cause I want to run my app both in <code>4.x &amp; 5.x iOS</code>.</p>