transitionFromView:toView:duration:options:completion: is not animating the transition - objective-c

Question

I have a view controller that displays the views of 2 sub view controllers in a given area of its view. The 2 sub view controllers are FlopVC and FipVC.
I want to animate the transition from one sub view to the other. The code I'm using is:
-(IBAction)flip:(id)sender{
UIViewController *newVC = nil;
if (self.isFlip) {
newVC = [[FlopVC alloc] initWithNibName:nil bundle:nil];
}else{
newVC = [[FipVC alloc] initWithNibName:nil bundle:nil];
}
newVC.view.frame = CGRectMake(120, 20, 240, 260);
[self.view addSubview:newVC.view];
[UIView transitionFromView:self.currentVC.view
toView:newVC.view
duration:0.9
options:UIViewAnimationTransitionFlipFromLeft
completion:^(BOOL finished) {
self.currentVC = newVC;
self.isFlip = ! self.isFlip;
}];
}
The sub views are swapped, but without any animation. What am I doing wrong?
PS the full project is here.

Answer 1

UIViewAnimationTransitionFlipFromLeft != UIViewAnimationOptionTransitionFlipFromLeft

Answer 2

if you are using the new iOS5 view container paradigm you need to do something along the lines of the following:
-(IBAction)flip:(id)sender{
UIViewController *newVC = nil;
if (self.isFlip) {
newVC = [[FlopVC alloc] initWithNibName:nil bundle:nil];
}else{
newVC = [[FipVC alloc] initWithNibName:nil bundle:nil];
}
newVC.view.frame = CGRectMake(120, 20, 240, 260);
// required for the new viewController container
self.currentVC willMoveToParentViewController:nil];
[self addChildViewController:newVC];
[self transitionFromViewController:self.currentVC
toViewViewController:newVC.view
duration:0.9
options: UIViewAnimationOptionTransitionFlipFromLeft
animations:nil
completion:^(BOOL finished) {
// required for the new viewController container
[self.currentVC removeFromParentViewController];
[newVC didMoveToParentViewController:self];
self.currentVC=newVC;
}];
}
reference the section Implementing a Container View Controller and the 2011 WWDC videos on UIViewController containers for more info.

Answer 3

Here is working code that (by sheer coincidence) does exactly what you're describing. My two child vc's are stored in self->swappers. The integer cur keeps track of which one is currently showing. The spot in my interface where the subview is to go is marked by a view outlet, panel.
UIViewController* fromvc = [self->swappers objectAtIndex:cur];
cur = (cur == 0) ? 1 : 0;
UIViewController* tovc = [self->swappers objectAtIndex:cur];
tovc.view.frame = self.panel.bounds;
// must have both as children before we can transition between them
[self addChildViewController:tovc]; // "will" called for us
// note: when we call remove, we must call "will" (with nil) beforehand
[fromvc willMoveToParentViewController:nil];
[self transitionFromViewController:fromvc
toViewController:tovc
duration:0.4
options:UIViewAnimationOptionTransitionFlipFromLeft
animations:nil
completion:^(BOOL done){
// note: when we call add, we must call "did" afterwards
[tovc didMoveToParentViewController:self];
[fromvc removeFromParentViewController]; // "did" called for us
}];