Swift函数

函数定义

使用 func 定义一个函数。调用函数使用他的名字加 上小括号中的参数列表。使用 -> 分隔参数的名字和 返回值类型。

函数声明：

func greet(name: String, day: String) -> String {
return "Hello \(name),today is \(day)."

} 

函数调用：greet("Bob", "Tuesday")

无返回值函数

func sayGoodbye(personName: String) {
println("Goodbye, \(personName)!")
}
sayGoodbye("Tony")

多返回值函数

使用元组类型返回多个值：

func count(string: String) -> (vowels: Int, consonants:Int, others: Int) {
var vowels = 0,consonants = 0, others= 0 for character in string {
switch String(character).lowercaseString {
case "a","e", "i","o", "u":
++vowels
case "b","c", "d","f", "g", "h", "j", "k", "l", "m","n", "p","q", "r","s", "t", "v", "w","x", "y", "z":
++consonants default:
++others
}
}
return (vowels, consonants, others)
}
let total = count("somearbitrary string!")
println("\(total.vowels) 元音 , \(total.consonants) 辅 音")

嵌入函数

函数嵌套： 相当于函数指针

func chooseStepFunction(backwards: Bool) ->(Int) -> Int {
func stepForward(input: Int) -> Int { return input
+ 1 }
func stepBackward(input: Int) -> Int { return input
- 1 }
return backwards ? stepBackward : stepForward
}
var currentValue = -4
let               moveNearerToZero                    =
chooseStepFunction(currentValue> 0)
while currentValue != 0{
println("\(currentValue)... ")
currentValue = moveNearerToZero(currentValue)
}

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