title: Custom Container View Controller in iOS 5 needs addSubView to add child controller?
body: <p>I have 1 view controller acting as a CustomViewContainer and it has 2 child view controllers with only 1 added initially at launch.</p>
  
  <p>Invoking <code>addChildViewController</code> from the Container on the child and then a subsequent invoke of <code>didMoveToParentViewController</code> on the child doesn't display my child view on the screen. Instead, I still see the parent controller's view. </p>
  
  <pre><code>@implementation ContainerViewController // inherits from UIViewController
  - (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
  {
      LOG_METHOD_SIG();    
      if (self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil])
      {
          // ChildViewController is a subclass of UIViewController
          _childController = [[ChildViewController alloc] initWithNibName:nil bundle:nil];
      }
      return self;
  }
  
  - (void)viewDidLoad
  {
      [super viewDidLoad];
  
      [self addChildViewController:_childController];
  
      // Expected the following line to display the child controller's view
      [_childController didMoveToParentViewController:self];
  }
  </code></pre>
  
  <p>If I add <code>[self.view addSubview:_childController.view]</code> after <code>'addChildViewController'</code>, the view is shown. But I thought that the whole point of container view controllers was to avoid direct view manipulation.</p>
  
  <p>In the case where you're adding your first child view controller, could you call 'transitionFromViewController` and if so, what would be the 'from' view controller?</p>