title: viewWillAppear not invoked for subview controller
body: <p>I have an odd case -- a view controller that creates its own view in <code>loadView</code> and which is then added to an existing view.</p>
  
  <p>Here is the code that creates and adds the VC:</p>
  
  <pre><code>self.doneButtonViewController = [[DoneButtonViewController alloc] init];
  [self.view addSubview:self.doneButtonViewController.view];
  </code></pre>
  
  <p>This code is executed in <code>viewDidLoad</code> of the "parent" VC.</p>
  
  <p>The odd thing is that the <code>viewWillAppear</code> method of the added VC is never invoked (nor is <code>viewDidAppear</code>), but the <code>viewWillDisappear</code> method of the added VC <em>is</em> invoked (at the appropriate time), just as one would expect.</p>
  
  <p>Any clue as to why <code>viewWillAppear</code> is not getting invoked?</p>