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Swift7 - 循环、函数

Swift7 - 循环、函数

作者: 暗物质 | 来源:发表于2020-05-29 15:51 被阅读0次
    // for 循环
    let names = ["Anna", "Alex", "Brian", "Jack"]
    for name in names {
        print("Hello, \(name)!")
    }
    
    let numberOfLegs = ["spider": 8, "ant": 6, "cat": 4]
    for (animalName, legCount) in numberOfLegs {
        print("\(animalName)s have \(legCount) legs")
    }
    
    let base = 3
    let power = 10
    var answer = 1
    for _ in 1...power {
        answer *= base
    }
    print("\(base) to the power of \(power) is \(answer)")
    
    // 半开区间运算符 ..<
    let minutes = 60
    for tickMark in 0..<minutes {
        //不包括60
    }
    
    let minuteInteval = 5
    for tickMark in stride(from: 0, to: minutes, by: minuteInteval) {
        // (0, 5, 10, 15 ... 45, 50, 55)
    }
    
    let hours = 12
    let hourInterval = 3
    for tickMark in stride(from: 3, through: hours, by: hourInterval) {
        // 3, 6, 9, 12
    }
    
    // switch
    let somePoint = (1, 1)
    switch somePoint {
        case (0, 0):
            print("\(somePoint) is at the origin")
        case (_, 0):
            print("\(somePoint) is on the x-axis")
        case (0, _) :
            print("\(somePoint) is on the y-axis")
        case (-2...2, -2...2):
            print("\(somePoint) is inside the box")
        default:
            print("\(somePoint) is outside of the box")
    }
    
    let anotherPoint = (2, 0)
    switch anotherPoint {
        case (let x, 0):
            print("on the x-axis with an x value of \(x)")
        case (0, let y):
            print("on the y-axis with a y value of \(y)")
        case (let x, let y):
            print("somewhere else at (\(x), \(y))")
    }
    
    let yetAnotherPoint = (1, -1)
    switch yetAnotherPoint {
    case let (x, y) where x == y:
        print("(\(x), \(y)) is on the line x == y")
    case let (x, y) where x == -y:
        print("(\(x), \(y)) is on the line x == -y")
    case let (x, y):
        print("(\(x), \(y)) is just some arbitrary point")
    }
    
    //返回值是元组
    func minMax(array: [Int]) -> (min: Int, max: Int)? {
        if array.isEmpty { return nil }
        var currentMin = array[0]
        var currentMax = array[0]
        
        for value in array[1..<array.count] {
            if value < currentMin {
                currentMin = value
            } else if value > currentMax {
                currentMax = value
            }
        }
        return (currentMin, currentMax)
    }
    
    if let bounds = minMax(array: [8, -6, 2, 109, 3, 77]) {
        print("min is \(bounds.min) and max is \(bounds.max)")
    }
    
    //可变参数,一个函数最多只能拥有一个可变参数。
    func arithmeticMean(_ numbers: Double...) -> Double {
        var total: Double = 0
        for number in numbers {
            total += number
        }
        return total / Double(numbers.count)
    }
    arithmeticMean(1, 2, 3, 4, 5)
    
    //输入输出参数:函数可以修改参数的值,并且想要在这些修改在函数调用结束后仍然存在
    func swaoTwoInts(_ a: inout Int, _ b: inout Int) {
        let temporaryA = a
        a = b
        b = temporaryA
    }
    
    var someInt = 3
    var anotherInt = 104
    swap(&someInt, &anotherInt)
    print("someInt is now \(someInt), and anotherInt is now \(anotherInt)")
    
    
    //使用函数类型
    func addTwoInts(_ a: Int, _ b: Int) -> Int {
        return a + b
    }
    func multiplyTwoInts(_ a: Int, _ b: Int) -> Int {
        return a * b
    }
    //”定义一个叫做 mathFunction 的变量,类型是‘一个有两个 Int 型的参数并返回一个 Int 型的值的函数’,并让这个新变量指向 addTwoInts 函数”。
    var mathFunction: (Int, Int) -> Int = addTwoInts
    print("Result: \(mathFunction(2, 3))")
    mathFunction = multiplyTwoInts
    print("Result: \(mathFunction(2, 3))")
    
    func chooseStepFuntion(backward: Bool) -> (Int) -> Int {
        func stepForward(intput: Int) -> Int {
            return intput + 1
        }
        func stepBackward(input: Int) -> Int {
            return input - 1
        }
        return backward ? stepBackward : stepForward
    }
    var currentValue = -4
    let moveNearerToZero = chooseStepFuntion(backward: currentValue > 0)
    while currentValue != 0 {
        print("\(currentValue)...")
        currentValue = moveNearerToZero(currentValue)
    }
    print("Zero!")
    
    

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          本文标题:Swift7 - 循环、函数

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