ios - CATransaction completion being called immediately

Question

I'm trying to execute a completion-block after my CAAnimation has finished. However, it seems that animation block is called before my animation completes. The animation still happens correctly though.

[CATransaction begin];
[self.view.layer addAnimation:self.dropAndBounceAnimation forKey:@"appearance"];
[CATransaction setCompletionBlock:completionBlock];
[CATransaction commit];

The dropAndBounceAnimation is a CAKeyFrameAnimation on position.y, with a fixed duration.

Answer 1

I'm not sure if this really is the correct fix, but by setting the completion-block before adding the animation for the layer, the completion-block is consistently called at the correct time.

[CATransaction begin];
[CATransaction setCompletionBlock:completionBlock];
[self.view.layer addAnimation:self.dropAndBounceAnimation forKey:@"appearance"];
[CATransaction commit];