swift2 控制流

let numberOfLegs = ["spider": 8,"ant": 6,"cat": 4]
for (animalName,legCount) in numberOfLegs {
    print("(animalName)s have (legCount) legs")
}
// spiders have 8 legs
// ants have 6 legs
// cats have 4 legs

for var index = 0; index < 3; ++index {
    print("index is (index)")
}
// index is 0
// index is 1
// index is 2

var square = 0
var diceRoll = 0
while square < finalSquare {
    // 掷骰子
    if ++diceRoll == 7 { diceRoll = 1 }
    // 根据点数移动
    square += diceRoll
    if square < board.count {
        // 如果玩家还在棋盘上，顺着梯子爬上去或者顺着蛇滑下去
        square += board[square]
    }
}
print("Game over!")

repeat {
    // 顺着梯子爬上去或者顺着蛇滑下去
    square += board[square]
    // 掷骰子
    if ++diceRoll == 7 { diceRoll = 1 }
    // 根据点数移动
    square += diceRoll
} while square < finalSquare
print("Game over!")

let temperatureInFahrenheit = 90
if temperatureInFahrenheit <= 32 {
    print("It's very cold. Consider wearing a scarf.")
} else if temperatureInFahrenheit >= 86 {
    print("It's really warm. Don't forget to wear sunscreen.")
} else {
    print("It's not that cold. Wear a t-shirt.")
}
// 输出 "It's really warm. Don't forget to wear sunscreen."

let someCharacter: Character = "e"
switch someCharacter {
case "a","e","i","o","u":
    print("(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":
    print("(someCharacter) is a consonant")
default:
    print("(someCharacter) is not a vowel or a consonant")
}
// 输出 "e is a vowel"

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).")
// 输出 "There are millions and millions of stars in the Milky Way."

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")
}
// 输出 "(1,1) is inside 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,y):
    print("somewhere else at ((x),(y))")
}
// 输出 "on the x-axis with an x value of 2"

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")
}
// 输出 "(1,-1) is on the line x == -y"

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
default:
    description += " an integer."
}
print(description)
// 输出 "The number 5 is a prime number,and also an integer."

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!")