Instance Method

updateDraggingItemsForDrag(_:)

Invoked when the dragging images should be changed.

Declaration

optional func updateDraggingItemsForDrag(_ sender: NSDraggingInfo?)

Parameters

sender: The object sending the message; use this object to get details about the dragging operation.

Discussion

While a destination may change the dragging images at any time, it is recommended to wait until this method is called before updating the dragging images.

This allows the system to delay changing the dragging images until it is likely that the user will drop on this destination. Otherwise, the dragging images will change too often during the drag which would be distracting to the user.

During enumerateDraggingItemsWithOptions:forView:classes:searchOptions:usingBlock: you may set non-acceptable drag items images to nil to hide them or use the enumeration option of clearNonenumeratedImages If there are items that you hide, then after enumeration, you need to set the numberOfValidItemsForDrop to the number of non-hidden drag items. However, if the valid item count is 0, then it is better to return none from your implementation of draggingEntered(_:) and, or draggingUpdated(_:) instead of hiding all drag items during enumeration.