SwiftDemo

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: NSDictionary?) -> Bool
    {
        self.window = UIWindow(frame: UIScreen.mainScreen().bounds)

        var root=RootViewController(nibName: nil, bundle: nil)
        self.window!.rootViewController=root

        self.window!.backgroundColor = UIColor.whiteColor()
        self.window!.makeKeyAndVisible()
        return true
    }

RootViewController.swift中
// #pragma mark -- ViewControlle Life
    override func viewDidLoad()
    {
        super.viewDidLoad()

        self.view!.backgroundColor=UIColor.darkGrayColor()
        var btn=UIButton.buttonWithType(UIButtonType.System) as UIButton
        btn.frame=CGRectMake(120,150,80,80)
        btn.setTitle("click me",forState:UIControlState.Normal)
        btn.addTarget(self,action:"Clicked:",forControlEvents:UIControlEvents.TouchUpInside)
        btn.setTitleColor(UIColor.greenColor(),forState:UIControlState.Normal)
        self.view!.addSubview(btn)
    }

    // #pragm mark -- Action
    func Clicked(sender:UIButton)
    {
        //直接这样创建有bug
//        var alert=UIAlertView(title: "提示", message: "Clicked!", delegate: self, cancelButtonTitle: "确定")
//        alert.show()
        var alert = UIAlertView()
        alert.title = "提示"
        alert.delegate = nil
        alert.addButtonWithTitle("确定")
        alert.message = "Clicked!"
        alert.show()
    }