Swift教程之枚举语法

import Foundation

//MARK:-------枚举语法-----------
//不像 C 和 Objective-C 一样。Swift 的枚举成员在被创建时不会被赋予一个默认的整数值
enum CompassPoint
{
    case North
    case South
    case East
    case West
}
enum Planet
{
    case Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Nepturn
}

var directionToHead = CompassPoint.West
directionToHead = .East

switch directionToHead
{
    case .North:
        print("北方")
    case .South:
        print("南方")
    case .East:
        print("东方")
    case .West:
        print("西方")
    default:
        print("未知方向")
}

//MARK:-------实例值（Associated Values）-----------
//你能够定义 Swift 的枚举存储不论什么类型的实例值。假设须要的话。每一个成员的数据类型能够是各不同样的
enum Barcode
{
    case UPCA(Int, Int, Int)
    case QRCode(String)
}

var productBarcode = Barcode.UPCA(8, 85909_51226, 3)
productBarcode = .QRCode("ABCDEFGHIJKLMNOP")

switch productBarcode
{
    case let .UPCA(numberSystem, identifier, check):
        print("UPC-A with value of \(numberSystem), \(identifier), \(check).")
    case let .QRCode(productCode):
        print("QR code with value of \(productCode).")
}
// 输出 "QR code with value of ABCDEFGHIJKLMNOP.

//MARK:-------原始值（Raw Values）-----------
//原始值能够是字符串。字符，或者不论什么整型值或浮点型值。每一个原始值在它的枚举声明中必须是唯一的。当整型值被用于原始值，假设其它枚举成员没有值时，它们会自己主动递增。enum PlanetRaw: Int{    case Mercury = 1, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune}//使用枚举成员的toRaw方法能够訪问该枚举成员的原始值：let earthsOrder = PlanetRaw.Earth.rawValueprint(earthsOrder)// earthsOrder is 3//MARK:-----------GCD演示----------var array = ["jack", "rose", "jay", "grace"];//声明一个全局并发队列，类型是 dispatch_queue_t；DISPATCH_QUEUE_PRIORITY_DEFAULT为队列优先级，默觉得0var queue: dispatch_queue_t =  dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)//开启一个线程dispatch_async(queue, { () -> Void in        print(NSThread.currentThread().isMainThread ? "这是主线程" : "这是后台线程")    //第一个參数为次数。第三个參数 block块里面的形參是区分第几次。    dispatch_apply(array.count, queue, { (index:Int) -> Void in            print(String(index) + " --- " + array[Int(index)])    })    //回调主线程。运行UI更新    dispatch_async(dispatch_get_main_queue(), { () -> Void in                print(NSThread.currentThread().isMainThread ? "这是主线程" : "这是后台线程")    })})