类型 'NSNotification.Name' 没有成员 'UITextField'

Question

在 Swift 4.2 中出现以下错误，在 Swift 4.

中工作正常

Type 'NSNotification.Name' has no member 'UITextField'

这是我的错误代码。

NotificationCenter.default.addObserver(forName: NSNotification.Name.UITextField.textDidChangeNotification, object: textField, queue: OperationQueue.main) { (notification) in
            loginAction.isEnabled = textField.text != ""
        }

完整代码：

@IBAction func alertWithLogin(){

    let alertController = UIAlertController(title: "Please Enter Credential", message: nil, preferredStyle: .alert)

    // ADD ACTIONS HANDLER
    let loginAction = UIAlertAction(title: "Login", style: .default) { (_) in

        let loginTextField = alertController.textFields![0] as UITextField
        let passwordTextField = alertController.textFields![1] as UITextField

        // do something with after login
    }
    loginAction.isEnabled = false
    alertController.addAction(loginAction)

    let cancelAction = UIAlertAction(title: "Cancel", style: .cancel) { (_) in
        // do something
    }
    alertController.addAction(cancelAction)

    // ADD TEXT FIELDS
    alertController.addTextField { (textField) in
        textField.placeholder = "Email"
    }
    alertController.addTextField { (textField) in
        textField.placeholder = "Password"
        textField.isSecureTextEntry = true

        // enable login button when password is entered
        NotificationCenter.default.addObserver(forName: NSNotification.Name.UITextField.textDidChangeNotification, object: textField, queue: OperationQueue.main) { (notification) in
            loginAction.isEnabled = textField.text != ""
        }
    }

    // PRESENT
    present(alertController, animated: true)
}

Answer 1

textDidChangeNotification 是 UITextField（和 UITextView）的成员。

NotificationCenter.default.addObserver(
    self,
    selector: #selector(self.keyboardDidShow(notification:)),
    name: UITextField.textDidChangeNotification,
    object: nil)

Answer 2

        NotificationCenter.default.addObserver(forName: Notification.Name.UITextFieldTextDidChange, object: textField, queue: OperationQueue.main) { (notification) in
            //...
    }

在swift sdk中，所有的通知名称都应该是struct的扩展：Notification.Name

所以当使用Notification.Name时，你应该忽略Class名字(exc.UITextField)，输入"Notification.Name."然后输入一些你的名字(比如"TextF" ) 并使用 esc 显示自动完成

Answer 3

我遇到了同样的问题，

这是最简单的解决方案：

而不是使用forName: NSNotification.Name.UITextField.textDidChangeNotification

在forName:参数中这样使用：

NotificationCenter.default.addObserver(forName: UITextField.textDidChangeNotification, object: textField, queue: OperationQueue.main) { (notification) in
//Your code goes here...
        }

类型 'NSNotification.Name' 没有成员 'UITextField'

Type 'NSNotification.Name' has no member 'UITextField'

ios

nsnotificationcenter

swift4.2