UICollectionView performBatchUpdates: asserts unexpectedly if view needs layout?

Question

If I call -[UICollectionView performBatchUpdates:] from inside viewWillAppear:, inside viewDidAppear:, between these methods, or anytime t

Answer 1

This is expected behaviour and not a bug. From the documentation on performBatchUpdates:

If the collection view's layout is not up to date before you call this method, a reload may occur. To avoid problems, you should update your data model inside the updates block or ensure the layout is updated before you call performBatchUpdates(_:completion:).