I have a UITableView that displays a Group/Note hierarchy analogous to a Finder Folder/Files hierarchy. I have implemented Drag and Drop such that if I drag a Note to the Finder Desktop an HTML file is created of the Note, and if I drag a Group to the Finder Desktop a Text file is created of the Group's title. Here is the Helper Dragging extension that I've implemented:
// // Model+Dragging.swift // /* Abstract: Helper methods for providing and consuming drag-and-drop data. */ import UIKit import MobileCoreServices // Conditionalize Drag and Drop so it is not in iOS target. #if targetEnvironment(macCatalyst) extension Model { /** A helper function that serves as an interface to the data model, called by the implementation of the `tableView(_ canHandle:)` method. */ func canHandle(_ session: UIDropSession) -> Bool { // In order to enable dragging all text type files changed the class // loadable objects from NSString to my custom TEXTClass. return session.canLoadObjects(ofClass: TEXTClass.self) } /** A helper function that serves as an interface to the data model, called by the `tableView(_:itemsForBeginning:at:)` method. */ func dragItems(for indexPath: IndexPath) -> [UIDragItem] { let itemProvider = NSItemProvider() let item = self.getDisplayItem(for: indexPath.row) if item is Note { let note:Note = item as! Note let html = note.noteHTML let data = html?.data(using: .utf8) // Drag to finder creates an html file. itemProvider.suggestedName = note.title + ".html" itemProvider.registerDataRepresentation(forTypeIdentifier: kUTTypeData as String, visibility: .all) { completion in completion(data, nil) return nil } } else { let group:Group = item as! Group let title = group.title let data = title?.data(using: .utf8) // Drag to finder creates a text file. itemProvider.suggestedName = group.title + ".text" itemProvider.registerDataRepresentation(forTypeIdentifier: kUTTypeData as String, visibility: .all) { completion in completion(data, nil) return nil } } return [ UIDragItem(itemProvider: itemProvider) ] } } #endif
I would now like to change the result of dragging a Group to the Finder. Instead of creating a Text file from the drag data, I would like to create a Folder containing the Group's Notes.
Note: I am unconcerned with the task of assembling the Group/Notes hierarchies as Folder/Files hierarchies because I already have implemented such previously as a menu export command. My concern is where and how I can communicate it to the Finder in the Drag and Drop process.
As a first step I thought I would simply create an empty folder from the drag of a Group. So far, none of my experiments have been successful. Every variation of itemProvider.registerDataRepresentation(forTypeIdentifier: or
itemProvider.registerFileRepresentation(forTypeIdentifier: or
registerItem(forTypeIdentifier:loadHandler: that
I have tried has failed to produce anything but empty TEXT files, if they worked at all.
It is my understanding that itemProviders may provide directories instead of files, but I have been unable to find any examples of such.
My problem may be a lack of understanding of the syntax and usage of the NSItemProvider.LoadHandler completion
block.
Any Swift examples on point would be greatly appreciated!