I implemented CollectionViewDelegate : func collectionView(_ collectionView: UICollectionView, shouldBeginMultipleSelectionInteractionAt indexPath: IndexPath) -> Bool {     return true   }   func collectionView(_ collectionView: UICollectionView, didBeginMultipleSelectionInteractionAt indexPath: IndexPath) {     print("\(#function)")   }   func collectionViewDidEndMultipleSelectionInteraction(_ collectionView: UICollectionView) {     print("\(#function)")     self.setEditing(false)   } and they work like this. The weird part is here Why collectionView misses those part item? Everything that I implemented collectionview is the same as the apple document example except I made my own UICollectionViewCompositionalLayout. I thought they maybe selected but something working wrong in the cell when they show as selected but when I check with breakpoint actually they are not selected at all. ( function didSelectItemAt doesn't call in that indexPath)