Called to notify you when the drag operation ends.
- iOS 11.0+
The collection view that is tracking the dragged content.
The drop session object containing information about the data being dragged.
The collection view calls this method at the conclusion of a drag that was over the collection view at one point. Use it to clean up any state information that you used to handle the drag. This method is called regardless of whether the data was actually dropped onto the collection view.