覆盖 UITextView 的 CMD + Z 键命令

如何解决覆盖 UITextView 的 CMD + Z 键命令

是否可以覆盖 UITextView 对 cmd + z 和 cmd + shift + z 的处理？

我试过了

• 覆盖 keyCommand 属性，但永远不会调用选择器..
• 覆盖 undoManager，这也无济于事

class CustomTextView: UITextView {

    override var keyCommands: [UIKeyCommand]? {
       [
            // cmd + z (doesn't work)
            UIKeyCommand(input: "z",modifierFlags: [.command],action: #selector(undo)),// cmd + shift + z  (doesn't work)
            UIKeyCommand(input: "z",modifierFlags: [.command,.shift],action: #selector(redo)),// z (works)
            UIKeyCommand(input: "z",modifierFlags: [],action: #selector(z)),]
    }
     
    // this doesn't help   
    override var undoManager: UndoManager? { return nil }
        






    // undo
    @objc private func undo() {
        print("undo")
    }

    // redo
    @objc private func redo() {
        print("redo")
    }

    // z
    @objc private func z() {
        print("z")
    }   
}