灵活的 switch

灵活的 switch

　　Swift 中的

switch

支持各种各样的比较操作：

let vegetable = "red pepper" switch vegetable {
case "celery":
let vegetableComment = "Add some raisins and make ants on a log." case "cucumber", "watercress":
let vegetableComment = "That would make a good tea sandwich." case let x where x.hasSuffix ("pepper"):
let vegetableComment = "Is it a spicy \(x)?" default:
let vegetableComment = "Everything tastes good in soup."
}

　　其它循环 本文来自www.itxxz.com

　　

for-in

除了遍历数组也可以用来遍历字典：

let interestingNumbers = [
"Prime": [2, 3, 5, 7, 11, 13],
"Fibonacci": [1, 1, 2, 3, 5, 8],
"Square": [1, 4, 9, 16, 25],
]
var largest = 0 for (kind, numbers) in interestingNumbers {
for number in numbers {
if number > largest {
largest = number
}
}
}
largest

　　

while

循环和

do-while

循环： 本文来自www.itxxz.com

var n = 2 while n < 100 {
n = n * 2
}
n

var m = 2 do {
m = m * 2
} while m < 100
m

　　Swift 支持传统的

for

循环，此外也可以通过结合

..

（生成一个区间）和

for-in

实现同样的逻辑。

var firstForLoop = 0 for i in 0..3 {
firstForLoop += i
}
firstForLoop

var secondForLoop = 0 for var i = 0; i < 3; ++i {
secondForLoop += 1
}
secondForLoop

　　注意：Swift 除了

..

还有

...

：

..

生成前闭后开的区间，而

...

生成前闭后闭的区间。