When exactly do implicit animations take place in iOS?

Question

Everyone and every book claims that there are implicit animations happening in CALayer. However, every time I wanted to verify that so far, I end up with a hard-snap to the

Answer 1

Keep in mind that sublayers of a UIView's primary layer do not normally have the UIView as their delegate. Therefore, they participate in implicit animation unless you explicitly block this, even if you haven't provided a delegate to return a nil action in response to actionForLayer:forKey:.

So, one simple way to get implicit animation in a generic view is simply to add a sublayer that covers the primary layer.

Matt Neuberg's book Programming iOS 5 (currently in beta on Safari Books Online) explains this topic very lucidly.