Swift学习笔记(三)控制流

概述1.for-in 循环语句 for index in 1...5 { println("\(index) times 5 is \(index * 5)")} 2.如果你不需要序列中的每一个值,你可以使用下划线来代替 let base = 3let power = 10var answer = 1for _ in 1...power { answer *= base} 3.

1.for-in 循环语句

for index in 1...5 {   println("\(index) times 5 is \(index * 5)")}

2.如果你不需要序列中的每一个值,你可以使用下划线来代替

let base = 3let power = 10var answer = 1for _ in 1...power {    answer *= base}

3.使用for-in去迭代遍历数组

let names = ["Anna","Alex","Brian","Jack"]for name in names {//    println("Hello,\(name)!")}

4.for-in去迭代遍历字典

let numberOfLegs = ["spIDer": 8,"ant": 6,"cat": 4]for (animalname,legCount) in numberOfLegs {//    println("\(animalname)s have \(legCount) legs")}

5.for循环 (不能使用let,因为index自增)

for var index = 0; index < 3; ++index {    println("index is \(index)")}

6.If语句

var temperatureInFahrenheit = 30if temperatureInFahrenheit <= 32 {    println("It's very cold. ConsIDer wearing a scarf.")}

7.Switch

let someCharacter: Character = "e"switch someCharacter {case "a","e","i","o","u":    println("\(someCharacter) is a vowel")case "b","c","d","f","g","h","j","k","l","m","n","p","q","r","s","t","v","w","x","y","z":    println("\(someCharacter) is a consonant")default:    println("\(someCharacter) is not a vowel or a consonant")}

8.switch元组

let somePoint = (1, 1)switch somePoint {case (0, 0):    println("(0,0) is at the origin")case (_, 0):    println("(\(somePoint.0),0) is on the x-axis")case (0,_):    println("(0,\(somePoint.1)) is on the y-axis")case (-2...2, -2...2):    println("(\(somePoint.0),\(somePoint.1)) is insIDe the Box")default:    println("(\(somePoint.0),\(somePoint.1)) is outsIDe of the Box")}

9.switch的case中可以使用where

let yetAnotherPoint = (1,-1)switch yetAnotherPoint {case let (x,y) where x == y:    println("(\(x),\(y)) is on the line x == y")case let (x,y) where x == -y:    println("(\(x),\(y)) is on the line x == -y")case let (x,y):    println("(\(x),\(y)) is just some arbitrary point")}// prints "(1,-1) is on the line x == -y"

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