Extend the standard drag and drop support for text views to include custom types of content.
UIText classes provide built-in support for dragging and dropping text and images. You can extend this support to your own custom data types by adding a text drag delegate or text drop delegate to your views. Your text drag delegate adopts the
UIText protocol and is responsible for providing the items to be dragged. Your text drop delegate adopts the
UIText protocol and handles drops containing items with your custom data types.