Difficulty with Drag and Drop - swift

Question

I'm having difficulty understanding how to implement simple drag and drop in a macOS application. What I want to do is make a TextField that can accept a directory or file that is dropped onto it and capture the URL to that directory or file.
With the code shown below, my print("dragging entered") line does fire when I drag an object onto the TextField control, however when I release it the performDragOperation doesn't fire.
Can anyone please help me understand simple drag and drop?
Thanks
import Cocoa
class DropTextField: NSTextField {
var dragTypes : [NSPasteboard.PasteboardType] = [.fileURL, .URL]
override func draw(_ dirtyRect: NSRect) {
super.draw(dirtyRect)
// Drawing code here.
}
override func awakeFromNib() {
self.registerForDraggedTypes(dragTypes)
}
public override func prepareForDragOperation(_ sender: NSDraggingInfo) -> Bool {
return true
}
public override func draggingEntered(_ sender: NSDraggingInfo) -> NSDragOperation {
print("dragging engtered")
return NSDragOperation.copy
}
public override func performDragOperation(_ sender: NSDraggingInfo) -> Bool {
print("drag operation")
return true
}
}

Answer 1

Assign this custom class to the NSTextField object on the storyboard and create an outlet in the controller:
public class DragTextField: NSTextField {
public var completionHandler: (URL) -> Void = { fileURL in Swift.print(fileURL) }
public override func draggingEntered(_ sender: NSDraggingInfo) -> NSDragOperation { return NSDragOperation.copy }
public override func draggingUpdated(_ sender: NSDraggingInfo) -> NSDragOperation { return NSDragOperation.copy }
public override func performDragOperation(_ sender: NSDraggingInfo) -> Bool {
let pboard = sender.draggingPasteboard
if let fileURLFromClipboard = pboard.string(forType: NSPasteboard.PasteboardType.fileURL) {
let sourceFileURL = URL(string: fileURLFromClipboard)!
print(sourceFileURL)
completionHandler(sourceFileURL)
}
return true
}
public required init?(coder: NSCoder) {
super.init(coder: coder)
stringValue = "Drop File Here";
isEditable = false
wantsLayer = true;
layer?.backgroundColor = NSColor.blue.cgColor
// Register for file name drag
registerForDraggedTypes([NSPasteboard.PasteboardType.fileURL])
}
}
Usage:
class ViewController: NSViewController {
#IBOutlet weak var dropView: DragTextField!
override func viewDidLoad() {
super.viewDidLoad()
dropView.completionHandler = {
print("File Path: \($0)")
}
}
}