Swift 基本语法（七）— 枚举

Swift 里枚举翻身了，和类、结构体可以并列了，地位很高啦

//简单定义一个方向枚举， 也是用驼峰法命名， 枚举一般使用单数形式
enum CompassDirection {
    case north  //单个成员值不用加“,”
    case south
    case west, east  //多个成员值可以写在一行里，用“，”隔开
}
//匹配枚举
let direction = CompassDirection.west
switch direction {
case .north:
    print("North")
case .south:
    print("South")
case .west:
    print("west")
case .east:
    print("east")
}

这个貌似是新特性，我在老版本不支持这个协议呢。。

//枚举可以遵循一个CaseIteralble,就可以访问枚举的所有类型的集合
//enum EarthPlant : CaseIteralble {
//    case muxing, huoxing, tuxing, shuixng
//    case tianwangxing
//    case xiaoxingxing
//}
//let allCase = EarthPlant.allCases

//枚举关联值

enum BarCode {
    case lineCode(Int, Int, Int, Int) //条形码， 存储四个数字
    case qrCode(String) //二维码 存储一个字符串
}
//关联值直接使用
var code = BarCode.lineCode(3, 10256, 36526, 6)
code = BarCode.qrCode("ThisISTwoCode")
switch code {
case .lineCode(let firstNum, let SecondNum, let ThirdNum, let ForthNum):
    print("nums 1-4: \(firstNum, SecondNum, ThirdNum, ForthNum)")
case .qrCode(let erCode):
    print("qrCode = \(erCode)") //qrCode = ThisISTwoCode
}

//指定原始值

enum TableChart: String {
    case tab = "\t"
    case line = "\n"
    case kong = " "
}
print(TableChart.kong.rawValue)

//预设原始值  Int类型 顺序赋值
enum Plant : Int {
    case earth = 1, tuxing, muxing, shuixing, huoxing
}
print(Plant.muxing.rawValue) //3

let xing = Plant(rawValue: 5)
print(xing)  // Optional(__lldb_expr_75.Plant.huoxing)

枚举递归的使用：

//递归枚举  枚举前面要加 indirect
indirect enum CustomFunction {
    case num(Int) //一个数字
    case addFunction(CustomFunction, CustomFunction) //加法公示 两个数字
    case mutilpleFunc(CustomFunction, CustomFunction)  //乘法
}
//5 + 4  * 2
let num1 = CustomFunction.num(5)
let num2 = CustomFunction.num(4)
let num3 = CustomFunction.num(2)
let addExpretion = CustomFunction.addFunction(num1, num2)
let mupleExpretion = CustomFunction.mutilpleFunc(addExpretion, num3)
print(mupleExpretion)  //mutilpleFunc(__lldb_expr_130.CustomFunction.addFunction(__lldb_expr_130.CustomFunction.num(5), __lldb_expr_130.CustomFunction.num(4)), __lldb_expr_130.CustomFunction.num(2))

func eval(_ expression: CustomFunction) -> Int {
    switch expression {
    case .num(let value):
        return value
    case .addFunction(let first, let second):
        return eval(first) + eval(second)
    case .mutilpleFunc(let first, let second):
        return eval(first) * eval(second)
    }
}
print(eval(mupleExpretion)) // 18

以上的打印结果：

打印结果