swift _ 控制流

//: Playground - noun: a place where people can play

import UIKit

var str = "Hello, playground"

//For循环

//For in

for index in 1...5{

    print(index)

}

//如果你不需要知道区间内每一项的值，你可以使用下划线（_）替代变量名来忽略对值的访问

let power = 6

for _ in 1...power {

    print("++++++")

}

//元组遍历

let numberOfLegs = ["spider": 8, "ant": 6]

for (code,cont) in numberOfLegs{

    print(code)

    print(cont)

}

//let http = (4,"rrr")

//http.0

/**

 *  switch

 区间匹配

 case分支的模式也可以是一个值的区间

 */

let count = 3_000_000_000_000

let countedThings = "stars in the Milky Way"

var naturalCount: String

switch count {

case 0:

    naturalCount = "no"

case 1...3:

    naturalCount = "a few"

case 4...9:

    naturalCount = "several"

case 10...99:

    naturalCount = "tens of"

case 100...999:

    naturalCount = "hundreds of"

case 1000...999_999:

    naturalCount = "thousands of"

default:

    naturalCount = "millions and millions of"

}

print("There are \(naturalCount) \(countedThings).")

/**

 *  元组

 你可以使用元组在同一个switch语句中测试多个值。元组中的元素可以是值，也可以是区间。另外，使用下划线（_）来匹配所有可能的值

 */

let somePoint = (1, 1)

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")

}

/**

 *  值绑定

 case分支的模式允许将匹配的值绑定到一个临时的常量或变量，

 这些常量或变量在该 case分支里就可以被引用了——这种行为被称为值绑定（value binding）。

 */

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, y):

    print("somewhere else at (\(x), \(y))")

}

/**

 *  Where

 case分支的模式可以使用where语句来判断额外的条件。

 */

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")

}

/**

 * 控制转移语句

 控制转移语句改变你代码的执行顺序，通过它你可以实现代码的跳转。Swift有四种控制转移语句。

 continue

 break

 fallthrough

 return

 */

let puzzleInput = "great minds think alike"

var puzzleOutput = ""

for character in puzzleInput.characters {

    switch character {

    case "a", "e", "i", "o", "u", " ":

        print("1")

       continue

    default:

        puzzleOutput.append(character)

    }

}

let numberSymbol: Character = "三"  //简体中文里的数字 3

var possibleIntegerValue: Int?

switch numberSymbol {

case "1", "١", "一", "๑":

    possibleIntegerValue = 1

case "2", "٢", "二", "๒":

    possibleIntegerValue = 2

case "3", "٣", "三", "๓":

    possibleIntegerValue = 3

case "4", "٤", "四", "๔":

    possibleIntegerValue = 4

default:

    break

}

if let integerValue = possibleIntegerValue {

    print("The integer value of \(numberSymbol) is \(integerValue).")

} else {

    print("An integer value could not be found for \(numberSymbol).")

}

/**

 *  贯穿

 fallthrough

 注意:

  fallthrough关键字不会检查它下一个将会落入执行的 case中的匹配条件。

 fallthrough简单地使代码执行继续连接到下一个 case中的执行代码，这和 C 语言标准中的switch语句特性是一样的

 */

//fallthrough

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

case 1:

    description += "34"

default:

    description += " an integer."

}

print(description)

/**

 * 带标签的语句

 

 */

let finalSquare = 25

var board = [Int](count: finalSquare + 1, repeatedValue: 0)

board[03] = +08; board[06] = +11; board[09] = +09; board[10] = +02

board[14] = -10; board[19] = -11; board[22] = -02; board[24] = -08

var square = 0

var diceRoll = 0

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]

    }

}

print("Game over!")

/*

 注意:

 如果上述的break语句没有使用gameLoop标签，那么它将会中断switch代码块而不是while循环体。

 使用gameLoop标签清晰的表明了break想要中断的是哪个代码块。 

 同时请注意，当调用continue gameLoop去跳转到下一次循环迭代时，

 这里使用gameLoop标签并不是严格必须的。因为在这个游戏中，只有一个循环体，

 所以continue语句会影响到哪个循环体是没有歧义的。然而，continue语句使用gameLoop标签也是没有危害的。

 这样做符合标签的使用规则，同时参照旁边的break gameLoop，能够使游戏的逻辑更加清晰和易于理解。

 */