OC转Swift之基础篇（二）--函数

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//函数

//老规矩“hello world”敬上

//函数最多只有一个可变参数（strings）放在最后一个参数

func joinStr(seperator:Character=",",strings:String...)->String{

var result:String =""

for (index,element) in strings.enumerated() {

if index !=0 {

result.append(seperator)

}

result += element

}

return result

}

let result = joinStr(seperator:" ", strings:"Hello","world","!")

print(result)

//多层函数的嵌套

func fn()->(Int,Int)->Int{

func minus(a:Int,b:Int)->Int{

return a-b

}

returnminus;

}

let minus =fn()

print(minus(10,5))

func calculate(num1:Int,num2:Int,fn:(Int,Int)->Int)->Int{

return fn(num1,num2)

}

print(calculate(num1:1, num2:2, fn: minus))

//方法与UI结合 textField添加内容监听方法方法写在viewDidLoad之外

//全局变量写在class之外

let showLabel =UILabel.init()

let textField =UITextField.init(frame:CGRect.init(x:20, y: 80, width:120, height:30));

textField.keyboardType =UIKeyboardType.decimalPad

textField.borderStyle =UITextBorderStyle.roundedRect

textField.font =UIFont.systemFont(ofSize:15)

textField.textColor =UIColor.darkGray;

textField.placeholder ="请输入内容"

textField.addTarget(self, action:#selector(FuncViewController.textFieldDidChange), for: UIControlEvents.editingChanged)

view.addSubview(textField)

showLabel.frame =CGRect.init(x: textField1.frame.minX, y: textField2.frame.maxY+10, width: textField1.frame.width, height:textField1.frame.height)

showLabel.text ="输入的内容"

showLabel.font =UIFont.systemFont(ofSize:15)

showLabel.textColor =UIColor.lightGray

showLabel.textAlignment =NSTextAlignment.left

view.addSubview(showLabel)

func textFieldDidChange(textField:UITextField){

var filePath =String(#file)!

let paths:[String] = filePath.components(separatedBy:"/")

filePath = paths.last!

print("<"+filePath+" : "+String(#line)+"> "+String(textField.text!))

showLabel.text = textField.text

}

//闭包

//闭包就是函数代码块，对函数进行简化隐藏return关键字 $0...$n表示第n个参数

let res =calculate(num1:1, num2:2, fn: {

$0-$1

})

print(res)

//闭包就是捕捉一定作用域的常量或者变量进而闭合并包裹着

func add(total:Int,step:Int)->()->Int{

var total = total

func fn()->Int{

total = total+step

return total

}

returnfn

}

let a =add(total:0, step:2)

print(a())

/**可在方法前此声明，告诉编译器此方法可以不接收返回值 **/

@discardableResult

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