Swift学习 --- 2.5控制流

for循环

<span style="font-size:18px;">
//1.swift提供了可以以区间的形式遍历的方法
        for item in 1...5 {
            println(item)
        }
        
        //2.闪光点 : 你可以使用下划线（_）替代变量名来忽略对值的访问
        let base = 3
        let power = 10
        var answer = 1
        for _ in 1...power {
            answer *= base
        }
        println("\(base) to the power of \(power) is \(answer)")
        // 输出 "3 to the power of 10 is 59049"
        
        //3.遍历字典
        var dict = ["key1" : 1 ,"key2" : 2,"key3" : 3]
        for (key1 ,value1) in dict {
            println(key1+"\(value1)")
        }
        
        //4.遍历字符串
        for char in "hello" {
            println(char)
        }
    
        //5.在初始化表达式中声明的常量和变量（比如var index = 0）只在for循环的生命周期里有效。如果想在循环结束后访问index的值，你必须要在循环生命周期开始前声明index。
        var index: Int
        for index = 0; index < 3; ++index {
            println("index is \(index)")
        }
        // index is 0
        // index is 1
        // index is 2
        println("The loop statements were executed \(index) times")
        // 输出 "The loop statements were executed 3 times

</span>

switch

<span style="font-size:18px;">
//1.switch 可以case 多个条件
        var intNum = 1
        switch intNum {
        case 1,3,5,7,9 :
                println("1")
                println("123")
        case 2,4,6,8,10 :
            println("2")
        default:
            println("other")
        }
        
        //2.switch 可以判断区间
        var intNum2 = 201
        switch intNum2 {
        case 1...200 :
            println("<200")
        case 201...500:
            println("200< && <500")
        default :
            println("other")
        }
        
        //3.switch 判断元组,用作point的判断太合适了!!!
        var point = (x : 110,y : 99)
        switch point {
        case (0..100 , 0..100 ):
            println("左上角")
        case (220..320 , 0..100 ) :
            println("右上角")
        case (0..100 , 380..480) :
            println("左下角")
        case (220..320 , 380..480) :
            println("右下角")
        case (_,_) :// _ 可以代表所有值
            println("中间")
        default :
            println("error")
        }
        
        //4.可以绑定值
        let anotherPoint = (2, 0)
        switch anotherPoint {
        case (let x, 0):
            println("on the x-axis with an x value of \(x)")
        case (0, let y):
            println("on the y-axis with a y value of \(y)")
        case let (x, y):
            println("somewhere else at (\(x), \(y))")
        }
        // 输出 "on the x-axis with an x value of 2"

</span>

<span style="font-size:18px;">//5.switch 判断元组 , 用where 做判断条件
        var point1 = (10,99)
        switch point1 {
            case let (x, y) where x < 100 && y < 100:
            println("左上角")
            case let (x, y) where 220 < x && x < 320 && y < 100:
            println("右上角")
            case let (x, y) where x < 100 && y < 480 && y > 380:
            println("左下角")
            case let (x, y) where 200 < x && x < 100 && y < 480 && y > 380:
            println("右下角")
            case (_,_) :// _ 可以代表所有值
            println("中间")
            default :
            println("error")


</span>

<span style="font-size:18px;">
//6. 使用贯穿来进入下一个case
let integerToDescribe = 5
var description = "The number \(integerToDescribe) is"
switch integerToDescribe {
case 2, 3, 5, 7, 11, 13, 17, 19:
    description += " a prime number, and also"
    fallthrough
default:
    description += " an integer."
}
println(description)
// 输出 "The number 5 is a prime number, and also an integer."</span>

<span style="font-size:18px;">//7 . 标签

gameLoop: while square != finalSquare {
    if ++diceRoll == 7 { diceRoll = 1 }
    switch square + diceRoll {
    case finalSquare:
        // 到达最后一个方块，游戏结束
        break gameLoop
    case let newSquare where newSquare > finalSquare:
        // 超出最后一个方块，再掷一次骰子
        continue gameLoop
    default:
        // 本次移动有效
        square += diceRoll
        square += board[square]
    }
}
println("Game over!")</span>