Swift9 - 枚举

//#  枚举成员的遍历
enum Beverage: CaseIterable {
    case coffee, tea, juice
}

let numberOfChoices = Beverage.allCases.count
print("\(numberOfChoices) beverages available")
// 打印“3 beverages available”
for beverage in Beverage.allCases {
    print(beverage)
}

// 定义表示两种商品条形码的枚举：
enum Barcode {
    case upc(Int, Int, Int, Int)
    case qrCode(String)
}

var productBarcode = Barcode.upc(8, 85999, 55564, 3)
productBarcode = Barcode.qrCode("ABCDEFGHIJKLMN")

switch productBarcode {
    case let .upc(numberSystem, manufacturer, product, check):
        print("UPC: \(numberSystem), \(manufacturer), \(product), \(check).")
    case let .qrCode(productCode):
    print("QR code: \(productCode).")
}


//## 原始值 rawValue
//原始值始终不变。关联值是创建一个基于枚举成员的常量或变量时才设置的值，枚举成员的关联值可以变化。
enum Planet: Int {
    case mercury = 1, venus, earth, mars, jupiter, saturn, uranus, neptune
}
enum CompassPoint: String {
    case north, south, east, west
}

let positionToFind = 11
if let somePlanet = Planet(rawValue: positionToFind) {
    switch somePlanet {
    case .earth:
        print("Mostly harmless")
    default:
        print("Not a safe place for humans")
    }
}else {
    print("There isn't a planet at position \(positionToFind)")
}

//可以在枚举成员前加上 indirect 来表示该成员可递归。