UIPercentDrivenInteractiveTransition does not interpolate transform property - ios7

Question

I'm currently trying to do an Interactive Transition between two view controllers. It is a dismissed interactive animation. I use a subclass of UIPercentDrivenInteractiveTransition and perform the following animation implemented in another object animator.
I do not succeed into make the interaction interpolating the transform property of the toVC view.
- (void) animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext
{
NSLog(#"Animate!!");
//Basic container
UIViewController *fromVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
UIViewController *toVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
fromVC.view.frame = [transitionContext initialFrameForViewController:fromVC];
toVC.view.frame = [transitionContext finalFrameForViewController:fromVC];
toVC.view.transform = CGAffineTransformMakeScale(0.9, 0.9);
//[transitionContext.containerView insertSubview:toVC.view belowSubview:fromVC.view];
NSTimeInterval duration = [self transitionDuration:transitionContext];
[UIView animateWithDuration:duration animations:^{
[fromVC beginAppearanceTransition:NO animated:YES];
fromVC.view.frame = CGRectMake(0, CGRectGetHeight(fromVC.view.frame), CGRectGetWidth(fromVC.view.frame), CGRectGetHeight(fromVC.view.frame));
toVC.view.transform = CGAffineTransformIdentity;
[toVC beginAppearanceTransition:YES animated:YES];
} completion:^(BOOL finished){
[transitionContext completeTransition:![transitionContext transitionWasCancelled]];
if(finished)
{
[fromVC endAppearanceTransition];
[toVC endAppearanceTransition];
}
}];
}
I would like to make the toVC starting with a scale and finish to fit the screen while the fromVC is sliding from top to bottom.
The sliding is correctly interpolates but the transform is simply done but do not interpolate.
Where is the error

Answer 1

I ran into this issue as well. For me, the solution was transforming a snapshot of toVC.view instead of toVC.view. I'm unsure why this was necessary though.
You can take the snapshot using snapshotViewAfterScreenUpdates:. You'll also need to set toVC.view's transform to CGAffineTransformIdentity and hide it before the animation starts. Then, unhide it in the completion block.