使用嵌套函数作为动作的选择器 - swift

Question

这是我的代码：

func didSelectLabel() {

    let label = UILabel(frame: CGRect(x: 0, y: 0, width: 50, height: 30))

    label.center = viewForEdit.center
    label.textAlignment = .center
    label.isUserInteractionEnabled = true

    func userDragged(gesture: UIPanGestureRecognizer) {

        let loc = gesture.location(in: self.viewForEdit)
        label.center = loc

    }

    gesture = UIPanGestureRecognizer(target: self, action: userDragged(gesture:))
    label.addGestureRecognizer(gesture)

    let alert = UIAlertController(title: "Write your text", message: "", preferredStyle: .alert)
    let continueAction = UIAlertAction(title: "Continue", style: .default) { (UIAlertAction) in

        label.text = alert.textFields?[0].text

    }

    let cancelAction = UIAlertAction(title: "Cancel", style: .cancel, handler: nil)
    alert.addTextField { (textField) in

        textField.placeholder = "Write here"

    }

    alert.addAction(continueAction)
    alert.addAction(cancelAction)

    present(alert, animated: true, completion: nil)

    self.viewForEdit.addSubview(label)

}

我想使用

func userDragged(手势: UIPanGestureRecognizer)

作为

的选择器

gesture = UIPanGestureRecognizer(target: self, action: userDragged(gesture:))

问题是如果我运行代码它会崩溃说

由于未捕获的异常“NSInvalidArgumentException”而终止应用程序，原因：“-[TestApp.ViewControllerEditor userDragged:]：无法识别的选择器发送到实例 0x7fc6b3c282b0”

P.S. 我不能将函数“userDragged(gesture:)”放在函数“didSelectLabel()”之外，因为如果这样做，“label.center = loc”会返回错误。这是因为在函数 'didSelectLabel()' 内部调用了 'label'

Answer 1

最简单的方法是将你的函数移到didSelectLabel之外，并将其更改为：

func userDragged(gesture: UIPanGestureRecognizer) {
    let loc = gesture.location(in: self.viewForEdit)
    let label = gesture.view as? UILabel
    label?.center = loc

}