Swift_控制流

Swift_控制流

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for-in 循环

//for-in 循环
fileprivate func testForIn() {
    //直接循环提取内部数据
    //[1,5]
    for index in 1...5 {
        print("\(index) times 5 is \(index * 5)")
    }

    //不需要提取数据 只需要循环次数
    let base = 2
    let power = 3
    var answer = 1
    for _ in 1...power {
        answer *= base
    }
    print("\(base) to the power of \(power) is \(answer)")

    //array遍历
    let array = ["XuBaoAiChiYu", "1045214799"]
    for item in array {
        print("array:\(item)!")
    }

    //Dictionary遍历
    let dict = ["name":"XuBaoAiChiYu", "QQ":"1045214799"]
    for (key, value) in dict {
        print("key:\(key);value:\(value)")
    }

    /*  print

     1 times 5 is 5
     2 times 5 is 10
     3 times 5 is 15
     4 times 5 is 20
     5 times 5 is 25
     2 to the power of 3 is 8
     array:XuBaoAiChiYu!
     array:1045214799!
     key:name;value:XuBaoAiChiYu
     key:QQ;value:1045214799

     */
}

while循环

//while循环
fileprivate func testWhile() {
    //先执行while条件判断 后执行内部代码
    let count = 4
    var index = 0
    while index < count {
        index += 1
        print("while:\(index)")
    }

    /*  print

     while:1
     while:2
     while:3
     while:4

     */
}

repeat-while循环

//repeat-while循环
fileprivate func testRepeatWhile() {
    //执行内部代码后判断条件
    let count = 4
    var index = 0
    repeat {
        index += 1
        print("RepeatWhile:\(index)")
    } while index < count

    /*  print

     RepeatWhile:1
     RepeatWhile:2
     RepeatWhile:3
     RepeatWhile:4

     */
}

if 判断

//if 判断
fileprivate func testIf() {
    //一个条件一个条件的判断 当条件为真时 执行内部程序
    let temp = 90
    if temp <= 32 {
        //不执行
    } else if temp >= 86 {
        print("执行")
    } else {
        //不执行
    }

    /*  print

     执行

     */
}

swich判断

//swich判断
fileprivate func testSwitch() {
    //基本switch (case不会穿透)

    let someCharacter: Character = "a"
    switch someCharacter {
    case "a":
        print("1")
    case "a", "b", "c":
        print("2") //这里不会输出 case找到后 执行完毕就返回(如果需要穿透 加 fallthrough)
    default:
        print("未找到")
    }

    /*  print

     1

     */
}

switch范围选择

//switch范围选择
fileprivate func testSwitchIntervalMatching() {
    //范围选择
    let approximateCount = 2
    switch approximateCount {
    case 1..<5:
        print("[1, 5)")
    case 5..<10:
        print("[5, 10)")
    default:
        print("未找到")
    }

    /*  print

     [1, 5)

     */
}

switch元组选择

//switch元组选择
fileprivate func testSwitchTuples() {
    //元组选择 坐标轴测试
    let random = arc4random()//随机数
    let somePoint = (Int(random%3), Int(random%3))//随机数获取点
    switch somePoint {
    case (0, 0):
        print("(0, 0) is at the origin")
    case (_, 0):
        print("(\(somePoint.0), 0) is on the x-axis")
    case (0, _):
        print("(0, \(somePoint.1)) is on the y-axis")
    case (-2...2, -2...2):
        print("(\(somePoint.0), \(somePoint.1)) is inside the box")
    default:
        print("(\(somePoint.0), \(somePoint.1)) is outside of the box")
    }

    /*  print

     (2, 2) is inside the box

     */
}

switch值选择

//switch值选择
fileprivate func testSwitchValueBindings() {
    let random = arc4random()//随机数
    //值绑定 如果设置未知数 当匹配成功时 执行此代码
    let anotherPoint = (Int(random%3), Int(random%1))
    switch anotherPoint {
    case (let x, 0):
        print("\(x)，x匹配")
    case (0, let y):
        print("\(y)，y匹配")
    case let (x, y):
        print("(\(x), \(y))，其他")
    }

    /*  print

     1，x匹配

     */
}

switch值绑定和where

//switch值绑定和where
fileprivate func testSwitchValueBindingsWhere() {
    //使用where条件二次判断
    let random = arc4random()//随机数
    let yetAnotherPoint = (Int(random%3), Int(random%3))
    switch yetAnotherPoint {
    case let (x, y) where x < y:
        print("\(x) < \(y)")
    case let (x, y) where x > y:
        print("\(x) > \(y)")
    case let (x, y):
        print("\(x) = \(y)")
    }

    /*  print

     1 = 1

     */
}

continue

//continue
fileprivate func testContinue() {
    //跳过本次循环 继续执行下次循环
    for index in 1...5 {
        if index == 2 {
            continue
        }
        print("continue:\(index)")
    }

    /*  print

     continue:1
     continue:3
     continue:4
     continue:5

     */
}

break

//break
fileprivate func testBreak() {

    // 跳过当前for或者switch 继续执行
    for x in 1...5 {
        if x == 2 {
            break
        }
        print("break-x:\(x)")
    }
    print("break-for")

    let z = 0
    switch z {
    case 0:
        break;
    default:
        break;
    }
    print("break-switch")

    /*  print

     break-x:1
     break-for
     break-switch

     */
}

fallthrough

//fallthrough
fileprivate func testFallthrough() {
    //击穿：执行当前case内的代码 并执行下一个case内的代码
    let x = Int(arc4random()%1)//0
    switch x {
    case 0:
        print("0")
        fallthrough
    case  1:
        print("1")
        fallthrough
    default:
        break;
    }

    /*  print

     0
     1

     */
}

标签

//标签
fileprivate func testLabeledStatements() {
    //标签语句 可以直接跳到写标签行的代码
    var b = false
    go : while true {
        print("go")
        switch b {
        case true:
            print("true")
            break go //跳过go标签的代码
        case false:
            print("false")
            b = true
            continue go //继续执行go标签的代码
        }
    }

    /*  print

     go
     false
     go
     true

     */
}

提前退出

//提前退出
fileprivate func testEarlyExit() {
    //guard和if很像 当条件判断为假时 才执行else中的代码
    func greet(_ person: [String: String]) {
        guard let name = person["name"] else {
            print("no name")
            return
        }
        print("name: \(name)!")
    }

    greet([:])
    greet(["name": "XU"])

    /*  print

     no name
     name: XU!

     */
}

检查API可用性

//检查API可用性
fileprivate func testCheckingAPIAvailability() {
    if #available(iOS 9.1, OSX 10.10, *) {
        print("iOS 9.1, OSX 10.10, *")
    } else {
        print("低版本")
    }

    /*  print

     iOS 9.1, OSX 10.10, *

     */
}