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

Question

With Swift 4.2, getting following error, that was working fine with Swift 4.

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

Here is my error code.

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

Full Code:

@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 is a member of UITextField (and UITextView).

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