ios 7 - UIView animate method with delay is not delayed

ios 7 - UIView animate method with delay is not delayed

I'm currently testing new iOS 7 views controller transition. What i want
is a custom modal presenting transition that present your next view cut
into several strip from top off screen. Each strip should appear after an
incremental delay to give the desired effect.
So my code looks like this :
-
(void)presentModalWithContext:(id<UIViewControllerContextTransitioning>)context
{
UIView *inView = [context containerView];
UIView *fromView = [context
viewControllerForKey:UITransitionContextFromViewControllerKey].view;
UIView *toView = [context
viewControllerForKey:UITransitionContextToViewControllerKey].view;
NSTimeInterval stripTime = 1.0;
NSTimeInterval stripDelay = 1.0;
NSInteger stripCount = 10;
CGFloat stripHeight = toView.frame.size.height / stripCount;
for (NSInteger i = 0; i < stripCount; i++)
{
CGFloat offsetY = i*stripHeight;
CGRect snapRect = CGRectMake(0, offsetY, toView.frame.size.width,
stripHeight);
UIView *view = [toView resizableSnapshotViewFromRect:snapRect
afterScreenUpdates:YES withCapInsets:UIEdgeInsetsZero];
CGRect stripRect = CGRectMake(0, -(stripCount-i)*stripHeight,
snapRect.size.width, snapRect.size.height);
view.frame = stripRect;
[inView insertSubview:view aboveSubview:fromView];
NSTimeInterval interval = stripDelay*(stripCount-i);
[UIView animateWithDuration:stripTime delay:interval options:0
animations:^{
CGPoint center = view.center;
center.y += stripCount*stripHeight;
view.center = center;
} completion:^(BOOL finished) {
NSLog(@"complete");
if (i == stripCount-1)
[context completeTransition:YES];
}];
}
}
I've already checked initial and final position of each strip and already
is OK. My interval variable is also properly set at each loop.
But it seems that this is not delayed at all. All strips are moving
together, giving the impression that the complete view is moving.
A quick look to basic log shows that all animations are performed at the
same time :
2013-09-20 01:11:32.908 test_transition[7451:a0b] complete
2013-09-20 01:11:32.909 test_transition[7451:a0b] complete
2013-09-20 01:11:32.910 test_transition[7451:a0b] complete
2013-09-20 01:11:32.910 test_transition[7451:a0b] complete
2013-09-20 01:11:32.911 test_transition[7451:a0b] complete
2013-09-20 01:11:32.911 test_transition[7451:a0b] complete
2013-09-20 01:11:32.912 test_transition[7451:a0b] complete
2013-09-20 01:11:32.912 test_transition[7451:a0b] complete
2013-09-20 01:11:32.913 test_transition[7451:a0b] complete
2013-09-20 01:11:32.913 test_transition[7451:a0b] complete
Do someone is able to spot what's wrong here ?