Swift 的懒加载和计算型属性

lazy var name: String = {
    return "BY"
}()

lazy var name: String = { () -> String i
    return "BY"
}()

var name: string {
    return "BY"
}

var name: string {
    get {
        return "BY"
    }
}

struct Cuboid {
    var width = 0.0, height = 0.0, depth = 0.0
    var volume: Double {
        return width * height * depth
    }
}
let fourByFiveByTwo = Cuboid(width: 4.0, height: 5.0, depth: 2.0)
print("the volume of fourByFiveByTwo is \(fourByFiveByTwo.volume)")
// Prints "the volume of fourByFiveByTwo is 40.0"