Swift viewWillTransition not called

Question

I\'m creating a full screen image gallery using a UICollectionView. When the user rotates the device, I perform updates to the UICollectionView wit

Answer 1

I replaced

func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator)

by

func willTransition(to newCollection: UITraitCollection, with coordinator: UIViewControllerTransitionCoordinator)

and it works for me.