Open Radar

 
Summary:
A UIDynamicAnimator initialized using -initWithCollectionViewLayout: does not hold a strong reference to its collection view layout but attempts to message it when deallocated, causing a bad access crash if the collection view layout is deallocated before the dynamic animator.

Steps to Reproduce:
1. Allocate and initialize a UICollectionViewLayout.
2. Allocate and initialize a UIDynamicAnimator using -initWithCollectionViewLayout: and passing in the collection view layout from step 1.
3. Deallocate the collection view.
4. Deallocate the dynamic animator.

Expected Results:
Nothing; two objects are allocated and then deallocated with no effect on the behavior of the app at runtime.

Actual Results:
The app crashes in the dynamic animator's -dealloc method because it attempts to message the non-existant collection view layout.

Version:
iOS 7.0 (11A465)

Notes:
It is not clear what type of reference the dynamic animator currently keeps to its collection view layout, but it appears neither to be a strong reference nor a weak zeroing reference because in neither case would this crash occur. Thus, one possible solution to this problem would be to expose the animator's collection view layout as a weak, readonly property, as is done with its reference view. Another possible solution would be to expose the collection view layout as a strong, readwrite property, eliminating the need to create a new animator every time the collection view's layout is replaced.

Configuration:
This occurs on my iPhone 4S running iOS 7.0 (11A465) when using Xcode 5 on a Macbook Pro with Retina Display running OS X 10.8.5. (This also occurs on the iPhone simulator that comes with Xcode 5.)