Swift2.0学习三

概述Swift2.0学习三 枚举 在Swift中枚举值可以是任何类型 可选型的实质是枚举。 var webSite: Optional<String> = Optional.Some("imooc.com")webSite = .None 原始值Raw Value enum Month: Int { case January = 1 case February = 2 cas Swift2.0学习三 枚举

在Swift中枚举值可以是任何类型

可选型的实质是枚举。

var webSite: Optional<String> = Optional.some("imooc.com")webSite = .None

原始值Raw Value

enum Month: Int {    case January = 1    case February = 2    case march = 3    case April = 4    case May = 5    case June = 6    case July = 7    case August = 8    case September = 9    case October = 10    case November = 11    case December = 12}func monthsBeforeNewYear( month: Month ) -> Int {    return 12 - month.rawValue}

根据rawValue构建枚举，返回值是一个可选型

let input = 4let month = Month(rawValue: input)

关联值

在枚举中，每一种可能性可以和一种变量相连接。

enum ATMStatus {    case Success(Int)    case Error(String)}var balance = 1000func withdraw( amount: Int ) -> ATMStatus {    if balance >= amount {        balance -= amount        return .Success(balance)    }else {        return .Error("Not enough money")    }}let result = withdraw(100)switch result {case let .Success(newBalance):    print("\(newBalance) Yuan left in your account.")case let .Error(errorMessage):    print("Error: \(errorMessage)")}

递归枚举

使用indirect表示递归枚举

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

使用

let five = ArithmeticExpression.Number(5)let four = ArithmeticExpression.Number(4)let sum = ArithmeticExpression.Addition(five,four)let two = ArithmeticExpression.Number(2)let product = ArithmeticExpression.Multiplication(sum,two)func evaluate(Expression: ArithmeticExpression) -> Int {    switch Expression {    case let .Number(value):        return value    case let .Addition(left,right):        return evaluate(left) + evaluate(right)    case let .Multiplication(left,right):        return evaluate(left) * evaluate(right)}evaluate(product) //18

结构体

结构体中声明的常量不可改变
构造函数
给结构体设置储值，可以如下创建结构体

struct Location{    var latitude: Double = 0    var longitude: Double = 0}var location = Location()

使用init()函数，重写构造函数

struct Location{    let latitude: Double    let longitude: Double    init(coordinateString: String) {        let commaIndex = coordinateString.rangeOfString(",")!.startIndex        let firstElement = coordinateString.substringToIndex(commaIndex)        let secondElement = coordinateString.substringFromIndex(commaIndex.successor())        latitude = Double(firstElement)!        longitude = Double(secondElement)!    }}

可以使用如下方式构造结构体

let appleheadQuarterLocation = Location(coordinateString: "37.2,47.8")

此时默认的构造方法就无效了。

可失败的构造函数

init?(coordinateString: String) {    guard let commaIndex = coordinateString.rangeOfString(",")?.startIndex else{        return nil    }    guard let firstElement = Double(coordinateString.substringToIndex(commaIndex)) else{        return nil    }    guard let secondElement = Double(coordinateString.substringFromIndex(commaIndex.successor())) else {        return nil    }    self.latitude = firstElement    self.longitude = secondElement}

结构体和枚举是值类型 在Swift中Array Dictionary Set String Int float Double Bool都是结构体

总结

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