Swift语言精要 - 扩展(Extension)

extension Int {
    var doubled : Int {
        return self * 2
    }
    func multiplyWith(anotherNumber: Int) -> Int {
        return self * anotherNumber
    }
}

2.doubled // = 4
4.multiplyWith(32) // = 128

protocol Blinking {
    var isBlinking : Bool { get }
    var blinkSpeed: Double { get set }
    func startBlinking(blinkSpeed: Double) -> Void
}

extension Int : Blinking {
    var isBlinking : Bool {
        return false;
    }
    var blinkSpeed : Double {
        get {
            return 0.0;
        }
        set {
            // Do nothing
        }
    }
    func startBlinking(blinkSpeed : Double) {
        println("I am the integer \(self). I do not blink.")
    }
}

2.isBlinking // = false
2.startBlinking(2.0) // prints "I am the integer 2. I do not blink."