它不工作的原因是因为你传递给函数的某个值不正确。swift不像Objective-C，你可以把nil放在类类型的参数中，没有任何限制(可能是)。参数otherButtonTitles被定义为非可选的，其类型的末尾没有(?)。所以你必须传递一个具体的值给它。

使用此代码显示alertview

  let alertController = UIAlertController(title: "Hello  Coders", message: "your alert message", preferredStyle: .Alert)
        let defaultAction = UIAlertAction(title: "Close Alert", style: .Default, handler: nil)
        alertController.addAction(defaultAction)

        presentViewController(alertController, animated: true, completion: nil)

Swift显示警报使用UIAlertController

对于SWIFT4，我认为扩展UIViewController并创建一个可重用的确认控件是最优雅的方式。

你可以像下面这样扩展UIViewController:

extension UIViewController {

func AskConfirmation (title:String, message:String, completion:@escaping (_ result:Bool) -> Void) {
    let alert = UIAlertController(title: title, message: message, preferredStyle: UIAlertControllerStyle.alert)
    self.present(alert, animated: true, completion: nil)

    alert.addAction(UIAlertAction(title: "Ok", style: .default, handler: { action in
        completion(true)
    }))

    alert.addAction(UIAlertAction(title: "Cancel", style: .cancel, handler: { action in
        completion(false)
    }))
  }
}

那么你可以随时使用它:

 AskConfirmation(title: "YOUR MESSAGE TITLE", message: "YOUR MESSAGE") { (result) in
        if result { //User has clicked on Ok

        } else { //User has clicked on Cancel

        }
    }

如果你的目标是iOS 7和8，你需要这样的东西来确保你对每个版本都使用了正确的方法，因为UIAlertView在iOS 8中已弃用，但UIAlertController在iOS 7中不可用:

func alert(title: String, message: String) {
    if let getModernAlert: AnyClass = NSClassFromString("UIAlertController") { // iOS 8
        let myAlert: UIAlertController = UIAlertController(title: title, message: message, preferredStyle: .Alert)
        myAlert.addAction(UIAlertAction(title: "OK", style: .Default, handler: nil))
        self.presentViewController(myAlert, animated: true, completion: nil)
    } else { // iOS 7
        let alert: UIAlertView = UIAlertView()
        alert.delegate = self

        alert.title = title
        alert.message = message
        alert.addButtonWithTitle("OK")

        alert.show()
    }
}

显示UIAlertView在swift语言:-

Protocol UIAlertViewDelegate

let alert = UIAlertView(title: "alertView", message: "This is alertView", delegate:self, cancelButtonTitle:"Cancel", otherButtonTitles: "Done", "Delete")
alert.show()

显示UIAlertViewController在swift语言:-

let alert = UIAlertController(title: "Error", message: "Enter data in Text fields", preferredStyle: UIAlertControllerStyle.Alert)
alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.Default, handler: nil))
self.presentViewController(alert, animated: true, completion: nil)

下面是警报视图和动作表的可重用代码，只需写一行在应用程序的任何地方显示警报

class AlertView{

    static func show(title:String? = nil,message:String?,preferredStyle: UIAlertControllerStyle = .alert,buttons:[String] = ["Ok"],completionHandler:@escaping (String)->Void){
        let alert = UIAlertController(title: title, message: message, preferredStyle: preferredStyle)

        for button in buttons{

            var style = UIAlertActionStyle.default
            let buttonText = button.lowercased().replacingOccurrences(of: " ", with: "")
            if buttonText == "cancel"{
                style = .cancel
            }
            let action = UIAlertAction(title: button, style: style) { (_) in
                completionHandler(button)
            }
            alert.addAction(action)
        }

        DispatchQueue.main.async {
            if let app = UIApplication.shared.delegate as? AppDelegate, let rootViewController = app.window?.rootViewController {
                rootViewController.present(alert, animated: true, completion: nil)
            }

        }
    }
}

用法:

class ViewController: UIViewController {

    override func viewWillAppear(_ animated: Bool) {
        AlertView.show(title: "Alert", message: "Are you sure ?", preferredStyle: .alert, buttons: ["Yes","No"]) { (button) in
            print(button)
        }
    }

}