Swift 2 学习笔记 10.枚举

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枚举

• 枚举基础

enum Month {
    case January
    case February
    case March
    case April
    case May
    case June
    case July
    case August
    case September
    case October
    case November
    case December
}

enum Season {
    case Spring, Summer, Autumn, Winter
}

let month1 = Month.November
let month2: Month = .November

func season (month: Month) -> Season {
    switch month {
    case .March, .April, .May:
        return .Spring
    case .June, .July, .August:
        return .Summer
    case .September, .October, .November:
        return .Autumn
    case .December, .January, .February:
        return .Winter
    }
}

season(month: .November)

• 枚举之原始值

enum ProgrammingLanguage: String {
    case Swift = "Swift"
    case OC = "Objective-C"
    case C
    case Java
}

let pm1: ProgrammingLanguage = .OC
print(pm1.rawValue)  // "Objective-C"
let pm2: ProgrammingLanguage = .C
print(pm2.rawValue)  // "C"

• 枚举之关联值

enum ATMStatus {
    case Success(Int)
    case Error(String)
    case Waiting
}
// 余额 1000 元
var balance = 1000
// 取钱操作
func withdraw(amount: Int) -> ATMStatus {
    if balance >= amount {
        balance -= amount
        return .Success(balance)
    }else {
        return .Error("Not enought money")
    }
}

switch withdraw(amount: 800) {
case let .Success(newBalance):
    print("\(newBalance) Yuan left")
case let .Error(errorMessage):
    print("Error:\(errorMessage)")
case .Waiting:
    print("Waiting")
}

• 枚举递归

indirect enum ArithmeticExpression{
    case Numebr(Int)
    case Addition( ArithmeticExpression, ArithmeticExpression)
    case Multiplication( ArithmeticExpression, ArithmeticExpression)
}