viewWillAppear called twice with custom segue animation using transitionFromView

Question

I'm looking to perform a segue to replace the window's root view controller by another view controller using a curl up animation. The idea is that I have a SplashViewController being displayed for a couple of seconds before transitioning (performSegueWithIdentifier:) to the next one, LoginViewController, using the curl up animation.

I've created a custom UIStoryboardSegue class called AnimatedSegue. Here is the code of the overridden perform method:

- (void)perform
{
  UIViewController *source = self.sourceViewController;
  UIViewController *destination = self.destinationViewController;

  UIWindow *window = source.view.window;

  [UIView transitionFromView:source.view
                      toView:destination.view
                    duration:1.0
                     options:UIViewAnimationOptionTransitionCurlUp
                  completion:^(BOOL finished) {
                    [window setRootViewController:destination];
                  }];
}

It works fine except that in iOS 6 (apparently not in iOS 5) the viewWillAppear: method is being called twice on the destination view controller. It seems that it's called a first time during the transition and second time when it executes [window setRootViewController:destination];

Note that I don't want to use a navigation controller. The SplashViewController gets deallocated (as expected) once the transition is over.

Any ideas on how to fix my problem?

Answer 1

Answering to my own question in case it can help someone else...

I ended up using Core Animation's CATransition class to create the segue's animation instead of the UIView's animation methods.

Here's how my new perform method looks like:

- (void)perform
{
  UIViewController *source = self.sourceViewController;
  UIWindow *window = source.view.window;

  CATransition *transition = [CATransition animation];
  [transition setDuration:1.0];
  [transition setDelegate:self];
  [transition setTimingFunction:[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear]];
  [transition setType:@"pageCurl"];
  [transition setSubtype:kCATransitionFromBottom];

  [window.layer addAnimation:transition forKey:kCATransition];
  [window setRootViewController:self.destinationViewController];
}