从 UIAlertController 返回文本到扩展

Question

在 Swift 中，如何返回我写入 UIAlertController 文本字段的字符串，如果此 UIAlertController 在扩展中，则添加

通常，如果您将 UIAlertController 实现本地放在类中，则可以轻松传递文本，但是当警报进入扩展时，我不确定哪种方式可以返回文本。

例如，假设你有这个扩展：

extension UIViewController {
    func presentTextFieldAlert(title: String, message: String, textFieldPlaceholder: String ) {
        let alertController = UIAlertController(title: title, message: message, preferredStyle: .alert)
        let saveAction = UIAlertAction(title: "OK", style: UIAlertAction.Style.default) { _ -> Void in
            let urlTextField = alertController.textFields![0] as UITextField
            if urlTextField.text != nil { }
        }

        let cancelAction = UIAlertAction(title: "Cancel", style: .default)
        alertController.addTextField { (textField: UITextField!) -> Void in
            textField.placeholder = textFieldPlaceholder
        }
        alertController.addAction(saveAction)
        alertController.addAction(cancelAction)
        self.present(alertController, animated: true, completion: nil)
    }
}

进入你的课堂：

class Client: UIViewController {

    func showAlert() {
        self.presentTextFieldAlert(title: "Hello", message: "Write sth", textFieldPlaceholder: "Write here")
    }
}

如何将警报中的文本传递给视图控制器？

我试过这样的事情：

class Client: UIViewController {

    func showAlert() -> String {
        return self.presentTextFieldAlert(title: "Hello", message: "Write sth", textFieldPlaceholder: "Write here")
    }
}

但我认为这不是正确的方法。

Answer 1

使用完成处理程序。

extension UIViewController {
    func presentTextFieldAlert(title: String, message: String, textFieldPlaceholder: String, completion: @escaping (String?)->()) {
        let alertController = UIAlertController(title: title, message: message, preferredStyle: .alert)
        let saveAction = UIAlertAction(title: "OK", style: UIAlertAction.Style.default) { _ -> Void in
            let urlTextField = alertController.textFields![0] as UITextField
            completion(urlTextField.text)
        }

        let cancelAction = UIAlertAction(title: "Cancel", style: .default)
        alertController.addTextField { (textField: UITextField!) -> Void in
            textField.placeholder = textFieldPlaceholder
            completion(nil)
        }
        alertController.addAction(saveAction)
        alertController.addAction(cancelAction)
        self.present(alertController, animated: true, completion: nil)
    }
}

然后您可以将其用作：

class Client: UIViewController {

    func showAlert() {
        self.presentTextFieldAlert(title: "Hello", message: "Write sth", textFieldPlaceholder: "Write here") { (result) in
            if let result = result {
                // User entered some text and tapped OK.
            }
        }
    }
}