import UIKitclass ViewController: UIViewController , UIAlertViewDelegate {    @IBOutlet var label: UILabel?    @IBOutlet var btn: UIButton?        @IBAction func btnClick(AnyObject) {        showAlert()    }        func showAlert() {        let alert = UIAlertView()        alert.title = "Alert"        alert.delegate = self        alert.message = "Hello Apple"        alert.addButtonWithTitle("OK")        alert.addButtonWithTitle("Cancel")        alert.show()    }        override func viewDidLoad() {        super.viewDidLoad()        // Do any additional setup after loading the view, typically from a nib.    }    override func didReceiveMemoryWarning() {        super.didReceiveMemoryWarning()        // Dispose of any resources that can be recreated.    }    func alertView(alertView: UIAlertView!, clickedButtonAtIndex buttonIndex: Int) {        switch buttonIndex            {        case 0:            self.label?.text = "ok";        case 1:            self.label?.text = "cancel"        default:            println("alertView cancel!")        }    }}