Question

while coding in iOS 4.3 before, I found while add a view controller’s view to another view with [superview addSubView:controller.view], the controller instance will not receive the -viewWillAppear/viewDidAppear message, than I found same issue in some thread in stack overflow. After that, I manually call -viewWillAppear/-viewDidAppear as needed.

but, after upgrade to iOS 5.0, some frisky UIView behavior happened. Finally I found that in iOS 5, the [superview addSubView:controller.view] , will send a -viewWillAppear/-viewDidAppear message to the controller instance automatically, plus my manually calls, there are two duplicated message each time the controller action its behavior.

and I also found a similar issue: iOS 5 : -viewWillAppear is not called after dismissing the modal in iPad

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 .

Does anyone fix similar issues or find some guidelines about these difference. cause I want to run my app both in 4.x & 5.x iOS.

Answer 1

In iOS 4 you had to manually call -viewWillAppear, -viewWillDisappear, etc. when adding or removing a view from your view hierarchy. These are called automatically in iOS 5 if the view is being added or removed from the window hierarchy. Fortunately, iOS 5 has a method in UIViewController that you can override to revert the behaviour back to how it worked with iOS 4. Just add this to your UIViewController:

-(BOOL)automaticallyForwardAppearanceAndRotationMethodsToChildViewControllers {
   return NO;
}

This is probably the easiest solution as long as you’re supporting both iOS 4 and iOS 5. Once you drop support for iOS 4 you might consider modifying your code to use the newer approach when swapping views.

Edit 5 February 2012

Apparently this function requires the child view controller be added to the main view controller using the addChildViewController: method. This method doesn’t exist in iOS4, so you need to do something like this:

  if ([self respondsToSelector:@selector(addChildViewController:)] ) {
     [self addChildViewController:childViewController];
  }

Thanks to everyone who corrected me on this.