如何在Swift中注册UndoManager？

我在一个Playground中尝试了这一方法，它可以完美地工作：

class UndoResponder: NSObject {    @objc func myMethod() {        print("Undone")    }}var undoResponder = UndoResponder()var undoManager = UndoManager()undoManager.registerUndo(withTarget: undoResponder, selector: #selector(UndoResponder.myMethod), object: nil)undoManager.undo()