swift2.0笔记3

1. 枚举语法

//1.定义一个枚举类型//2.必须以大写字母开头//3.case创建新的枚举值enum SomeEnumeration{    //代码}

enum CompassPoint{    case South    case East    case North    case West}

//多个成员值可以出现在同一行上enum Planet {    case Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune}

var directionToHead = CompassPoint.WestdirectionToHead = .Northswitch directionToHead {    case .South:        print("It is South")    case .West:        print("It is west")    default:        print("Another direction")}

2. 枚举关联值

//1.定义一个Barcode枚举类型，一个成员是具有（Int,Int,Int,Int)类型关联值的UPCA，另一个成员是具有String类型关联值的QRCode//2.枚举类型的常亮和变量只能存储一个枚举值(和其关联值)enum Barcode{    case UPCA(Int,Int,Int,Int)    case QRCode(String)}var productBarcode = Barcode.UPCA(8, 85909, 51226, 3)  //枚举类型变量存储一个枚举值和其关联值productBarcode = .QRCode("ABCDEFGHIJKLMNOP")  //变量存储值被替换,因为只能存储一个枚举值及其关联值switch productBarcode {    case .UPCA(let numberSystem, let manufacturer, let product, let check):        print("UPC-A: \(numberSystem), \(manufacturer), \(product), \(check).")    case .QRCode(let productCode):        print("QR code: \(productCode).")}

3. 枚举原始值

//1.定义：枚举成员的默认值称为原始值//2.原始值的类型必须相同//3.原始值在枚举值中声明必须唯一enum ControlChar: Character{    case Tab = "\t"    case LineFeed = "\n"    case CarriageReturn = "\r"}

//关联值和原始值的区别//1.原始值在定义枚举值被预先填充的值，原始值是不变的//2.关联值是枚举类型的一个变量，这个变量是基于枚举成员的值，关联值是可以变化的enum PlanetAgain: Int {    case Mercury = 1, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune}let earthsOrder = PlanetAgain.Earth.rawValueprint(earthsOrder)//在上面的例子中, Plant.Mercury 的显式原始值为 1.Planet.Venus 的隐式原始值为 2.依次类推。enum CompassPointAgain: String {    case North, South, East, West}let sunsetDirection = CompassPointAgain.West.rawValueprint(sunsetDirection)//上面例子中, CompassPoint.South 拥有隐式原始值 South ,依次类推。

4. 使用原始值初始化枚举实例

//1.原始值构造器返回一个可选的枚举成员//2.下例中的possiblePnalet是可选的let possiblePnalet = PlanetAgain(rawValue: 7)print(possiblePnalet!)