[Swift][Cocoa] Drag&Drop したファイルのファイルパスを NSTextFeild に表示する

import Cocoa

class FileDragDropView: NSView {

    var acceptableTypes: Set<String> {
        return [NSURLPboardType]
    }
    var nonURLTypes: Set<String>  {
        return [String(kUTTypeText)]
    }
    let filteringOptions = [NSPasteboardURLReadingContentsConformToTypesKey:["public.text"]]
    var label: NSTextField?

    override func draw(_ dirtyRect: NSRect) {
        super.draw(dirtyRect)
    }

    override init(frame frameRect: NSRect) {
        super.init(frame: frameRect)
        setup()
    }

    required init?(coder: NSCoder) {
        super.init(coder: coder)
        setup()
    }

    override func awakeFromNib() {
        super.awakeFromNib()
        label = NSTextField(frame: NSRect(x: 20, y: 20, width: self.frame.width - 40, height: 40))
        label?.stringValue = ""
        label?.textColor = NSColor.black
        self.addSubview(label!)
    }

    func setup() {
        self.register(forDraggedTypes: Array(acceptableTypes))
    }

    func shouldAllowDrag(_ draggingInfo: NSDraggingInfo) -> Bool {
        var canAccept = false
        let pasteBoard = draggingInfo.draggingPasteboard()
        if pasteBoard.canReadObject(forClasses: [NSURL.self], options: filteringOptions) {
            canAccept = true
        } else if let types = pasteBoard.types, nonURLTypes.intersection(types).count > 0 {
            canAccept = true
        }
        return canAccept
    }

    override func draggingEntered(_ sender: NSDraggingInfo) -> NSDragOperation {
        let allow = shouldAllowDrag(sender)
        return allow ? .copy : NSDragOperation()
    }

    override func prepareForDragOperation(_ sender: NSDraggingInfo) -> Bool {
        let allow = shouldAllowDrag(sender)
        return allow
    }

    override func performDragOperation(_ sender: NSDraggingInfo) -> Bool {
        let pasteBoard = sender.draggingPasteboard() as NSPasteboard
        if let urls = pasteBoard.readObjects(forClasses: [NSURL.self], options: filteringOptions) as? [URL], urls.count > 0 {
            label?.stringValue = ""
            let files = pasteBoard.propertyList(forType: NSFilenamesPboardType) as! [String]
            for file in files {
                label?.stringValue += file + "\n"
            }
            return true
        }
        else if let types = pasteBoard.types, types.contains(NSFilenamesPboardType) {
            label?.stringValue = ""
            let files = pasteBoard.propertyList(forType: NSFilenamesPboardType) as! [String]
            for file in files {
                label?.stringValue += file + "\n"
            }
            return true
        }
        return false
    }
}