Swift---6.函数

2017-02-22  本文已影响11人  阿丶伦
func hello() {
     print("hello world!")
}
hello()
func appendStr (first:String,second:String) -> String {
     let string = first + second
     return string
}
var helloworld = appendStr(first: "hello ", second: "world!")
func hello (string:String) {
     print(string)
}
func hello() {
     print("hello")
}
hello()
hello(string: "test")
- 参数标签(Swift中,函数参数拥有一个标签名,用于外部调用时传入参数,若我们不想暴露参数名称,可以使用关键字```_```,则外部调用参数时,不会看到对应的参数名)
```
func appendStr (str1 first:String,str2 second:String) -> String {
    let string = first + second
    return string
}
print(appendStr(str1:"a", str2:"b"))
func appendStr (_ first:String,_ second:String) -> String {
    let string = first + second
    return string
}
print(appendStr("a", "b"))
```
- 参数默认值(Swift中,可以在定义传入参数时,为其添加默认值,若调用方法时不传入,则默认使用该值)
```
func num(first:Int = 11 , second:Int = 12) {
    print("\(first) + \(second) = \((first+second))")
}
num()
num(first:1)
num(first: 10, second: 10)
```
- 可变参数(当我们不确定传入参数个数时,我们可以使用可变参数来声明改函数可以传入不同数量的值作为参数,在参数类型后使用```...```即可)
```
func variableArguments(_ arguments:Int...) {
    var total = 0
    guard arguments.count>0 else {
        return
    }
    for number in arguments {
        total += number
    }
    print(total)
}
variableArguments(1,2,3,4,5,6)
variableArguments()
```
- 改变参数的值(我们知道传入的值是常量,不可改变,但如果我们想改变传入的值,可以使用```inout```关键字加在参数名类型前,注意,调用函数式,参数名前面需要加入```&```符号;同时,内部参数改变,外部的参数也会发生变化,且可变参数不可使用```inout```关键字,也不可传入常数作为参数)
```
func swapTwoInts(_ a:inout Int ,_ b:inout Int) {
    var tem = 0
    tem = a
    a = b
    b = tem
}
var a = 3
var b = 4
swapTwoInts(&a, &b)
print(a,b)
```
-
func addFunction(_ number1:Int , _ number2 : Int) -> Int {
       return number1 + number2
}
var function:(Int,Int) -> Int = addFunction
print(function(1,3))
func addFunction(_ number1:Int , _ number2 : Int) -> Int {
       return number1 + number2
}
var function:(Int,Int) -> Int = addFunction
func printAddFuctionResult (function:(Int,Int) -> Int,_ a:Int,_ b : Int) {
       function(a,b)
}
printAddFuctionResult(function: addFunction, 3, 5)
func addFunction() -> (Int,Int) -> Int {
       func returnFunc (_ a:Int , _ b:Int) ->Int {
           return a+b
       }
       return returnFunc
}
var function = addFunction()
var total = function(1,3)
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