How can I "pass" a persistent label in a custom transition animation in iOS8? - uiviewcontroller

Question

I have a custom transition animation between view controllers, and I want a UILabel to be (or appear) the same on both the fromViewController and the toViewController.
I tried the following:
toViewController.nameLabel = fromViewController.nameLabel;
In the context of the code below but got the following error :
[UINavigationController nameLabel]: unrecognized selector sent to
instance
What am I doing wrong?
- (void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext {
// Grab the from and to view controllers from the context
HC_ExercisePageVC *fromViewController = (HC_ExercisePageVC *)[transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
HC_TimerVC *toViewController = (HC_TimerVC *)[transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
if (self.presenting) {
fromViewController.view.userInteractionEnabled = NO;
[transitionContext.containerView addSubview:toViewController.view];
CGRect startFrame = endFrame;
startFrame.origin.y += 75;
toViewController.movingViews.frame = startFrame;
toViewController.nameLabel = fromViewController.nameLabel;
[UIView animateWithDuration:[self transitionDuration:transitionContext] animations:^{
toViewController.movingViews.frame = endFrame;
} completion:^(BOOL finished) {
[transitionContext completeTransition:YES];
}];
}
else {
Update: Following the suggestion by #Gavin, I replaced the code with:
// Grab the from and to view controllers from the context
HC_ExercisePageVC *fromViewController = (HC_ExercisePageVC *)[transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
UINavigationController *toViewControllerNavigation = (id)[transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
HC_TimerVC * toViewController = (HC_TimerVC *)toViewControllerNavigation.viewControllers.firstObject;
But when I do that I get error:
-[HC_TimerVC viewControllers]: unrecognized selector sent to instance
I always get hung up on how to handle navcontrollers...

Answer 1

Looks like your toViewController is contained within a UINavigationController, thus it is returning that as the destination.
So you'll need to grab the HC_TimerVC from the navigation controller:
- (void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext {
// Grab the from and to view controllers from the context
HC_ExercisePageVC *fromViewController = (HC_ExercisePageVC *)[transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
UINavigationController *toViewControllerNavigation = (id)[transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
HC_TimerVC * toViewController = toViewControllerNavigation.viewControllers.firstObject;
....