viewWillTransitionToSize coordinator ignores block

Question

Tried gaming the new rotation methods, I need to know if the device is being rotated in order to defer and cancel an action that is not required in the event of rotation.

-(void)viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator
{
    [super viewWillTransitionToSize:size withTransitionCoordinator:coordinator];

    _rotating = YES;

    [coordinator notifyWhenInteractionEndsUsingBlock:^(id<UIViewControllerTransitionCoordinatorContext> context) {
        _rotating = NO;
    }];
}

Seems straight forward and should work based on my interpretation of the documentation but apparently no. It seems that _rotating is set to YES and never gets set back to NO. Consequently, it seems my completion block is never called.

Answer 1

I had the same problem. I dived into the docs. The block you specify in notifyWhenInteractionEndsUsingBlock gets called when:

When a transition changes from interactive to non-interactive then handler is invoked.

However, rotation is not an interactive transition. Once it starts you cannot interact with it. That's why the handler is never called.

I ended up using animateAlongsideTransition:completion: method. It works like a charm.

- (void)viewWillTransitionToSize:(CGSize)size
       withTransitionCoordinator:(id <UIViewControllerTransitionCoordinator>)coordinator
{
    _rotating = YES;

    [super viewWillTransitionToSize:size
          withTransitionCoordinator:coordinator];

    [coordinator animateAlongsideTransition:nil
                                 completion:^(id<UIViewControllerTransitionCoordinatorContext> context)
     {
        _rotating = NO;
     }];
}