class SingletonA {

    static let sharedInstance = SingletonA()

    init() {
        println("AAA");
    }

}

class SingletonB {

    class var sharedInstance: SingletonB {
        struct Static {
            static let instance: SingletonB = SingletonB()
        }
        return Static.instance
    }

}

// Please note that internalNameOne and internalNameTwo are the
// parameters accessible in the myFunction scope. That is, of course,
// the internal parameter names

// Standard behaviour
func myFunction(internalNameOne: Int, internalNameTwo: Int) {}
myFunction(1, internalNameTwo: 2)

// Second parameter with different external name
func myFunction(internalNameOne: Int, externalNameTwo internalNameTwo: Int) {}
myFunction(1, externalNameTwo: 2)

// This is how # used to work for the first parameter
func myFunction(internalNameOne internalNameOne: Int, externalNameTwo internalNameTwo: Int) {}
myFunction(internalNameOne: 1, externalNameTwo: 2)

// First and second parameters have different external parameter names
func myFunction(externalNameOne internalNameOne: Int, externalNameTwo internalNameTwo: Int) {}
myFunction(externalNameOne: 1, externalNameTwo: 2)

// Bonus: omitting external parameter names
func myFunction(internalNameOne: Int, _ internalNameTwo: Int) {}
myFunction(1, 2)

class SecondViewController: UIViewController {

    var webview: UIWebView?

    override func viewWillAppear(animated: Bool) {
        let ua = UIWebView().stringByEvaluatingJavaScriptFromString("navigator.userAgent")!
        print("get ua \(ua)")
        NSUserDefaults.standardUserDefaults().registerDefaults(["UserAgent": " \(ua) HAHA\(arc4random())"])

        // 将老的容器干掉
        if let wv = webview {
            wv.removeFromSuperview();
        }
        print("create new webview")
        // 创建新的容器
        webview = UIWebView(frame: CGRect(x: 0, y: 0, width: 200, height: 500))
        view.addSubview(webview!)

        webview?.loadRequest(NSURLRequest(URL: NSURL(string: "http://localhost:8000/x")!))

    }

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
     //   let ua = webview.stringByEvaluatingJavaScriptFromString("navigator.userAgent += ' HBBBB'")!
     //   NSUserDefaults.standardUserDefaults().registerDefaults(["userAgent": "\(ua) HHHHBBBB"])

    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


}

enum Optional<T> {
  case None
  case Some(T)
}

let x: String? = nil 
// 相当于
let x = Optional<String>.None

let x: String？ = "hello"
// 相当于
let x = Optional<String>.Some("hello")

var y = x!  // 强制unwrap一个nil会抛异常
// 相当于
switch x {
  case .Some(let val): y = value
  case .None: /* Throw Error */
}

let x: String? = ....
if let y = x {
  // do something
}
// 相当于
switch x {
  case .Some(let y): // do something with y
  case None: break;
}

var display: UILabel?;
if let label = display {
  if let text = label.text {
    let x = text.hashValue
  }
}
// 相当于
if let x = display?.text?.hashValue {
  // ..
}

let s: String? = ...
if s != nil {
  display.text = s
} else {
  display.text = ""
}
// 相当于
display.text = s ?? ""