IOS: View Translation Animation. Proper way. - ios

Question

I'm implementing my own Navigation Controller and I'm faking the animation of adding the new view as in UINavigationContoller.
The following code works great, however if I move -addSubview:, before UIView animation call, it will animate in ios7, but not in ios6, the question is why? (I mean, why does it would make a difference, as animation will be scheduled and executed asynch, right? Or I might suppose It will somehow affect the starting state of animation?)
- (void)didAddViewControllerInNavigationStack:(NSArray*)navigationStack
{
if (self.activeViewController) {
[self.activeViewController viewWillDisappear:YES];
[self.activeViewController viewDidDisappear:YES];
}
self.activeViewController = navigationStack.firstObject;
if (!self.activeViewController) return;
CGRect windowRect = [[UIScreen mainScreen] bounds];
windowRect.origin.x = windowRect.size.width;
self.activeViewController.view.frame = windowRect;
[self.activeViewController viewWillAppear:YES];
[UIView transitionWithView:self.view
duration:0.32
options:UIViewAnimationOptionCurveEaseOut
animations:^ { self.activeViewController.view.frame = [[UIScreen mainScreen] bounds]; }
completion:^(BOOL isDone){[self.activeViewController viewDidAppear:YES];}];
[self.view addSubview:self.activeViewController.view];
[UIView commitAnimations];
}

Answer 1

From the documentation of transitionWithView:duration:options:animations:completion:, it is said you should add the subview inside the animation block:
The block you specify in the animations parameter contains whatever state changes you want to make. You can use this block to add, remove, show, or hide subviews of the specified view.
Also, you are calling commitAnimations without having called beginAnimations:context:. You are mixing things here. Block-based animation API does not need the begin-end API.
Your code should be:
[UIView transitionWithView:self.view
duration:0.32
options:UIViewAnimationOptionCurveEaseOut
animations:^ { [self.view addSubview:self.activeViewController.view]; self.activeViewController.view.frame = [[UIScreen mainScreen] bounds]; }
completion:^(BOOL isDone){[self.activeViewController viewDidAppear:YES];}];