swift閉包純代碼

做過swift開發的肯定要用到閉包，swift中的閉包就相當于OC裡面的block都是用于回調。

舉個簡單的例子，傳回兩個參數的和：

第一種 正常做法

//傳回兩個數的和
        func sum(numberOne number1:Int,numberTwo number2:Int)->Int
        {
            return (number1 + number2)
        }
        
        let sumTwoNumber = sum(numberOne: 1, numberTwo: 2)
           

第二種 使用閉包

var myCloure0:((Int,Int)->Int)?            //聲明一個閉包函數
        typealias MyCloureType = (Int,Int) -> Int  //類型取一個别名
        var myCloure:MyCloureType?
        
       //參數清單和真正的函數體之間使用關鍵字in來分割
        myCloure0 = {
            (num1:Int,num2:Int) -> Int in
            return num1+num2
        }
        myCloure = {
            (num1:Int,num2:Int) -> Int in
            return num1+num2
        }
        //執行閉包函數
        let sumInt:Int =  myCloure0!(10,10)
        let sumInt1:Int =  myCloure!(20,20)
        print("sumInt = \(sumInt) sumInt1 = \(sumInt1)")
           

列印：

sumInt = 20 sumInt1 = 40

我們發現閉包用起來也非常簡單，下面來看看閉包的回調傳值:

先定義兩個控制器  FirstViewController SecondViewController

first控制器:

class FirstViewController: UIViewController {

    
    var fisrtBtn:UIButton = {
        let button:UIButton = UIButton()
        button.backgroundColor = UIColor.redColor()
        button.setTitle("Go SecondViewController", forState: .Normal)
        button.layer.masksToBounds = true
        return button
    }()
    
    var secondLabel:UILabel = {
        let label:UILabel = UILabel()
        label.backgroundColor = UIColor.greenColor()
        label.text = "顯示Second中輸入的值"
        label.font = UIFont.systemFontOfSize(13.0)
        return label
    }()
    
    override func viewDidLoad() {
        super.viewDidLoad()

        fisrtBtn.frame = CGRectMake(50, 50, 200, 40)
        secondLabel.frame = CGRectMake(50, 100, 200, 40)
        fisrtBtn.addTarget(self, action:#selector(FirstViewController.fisrtBtnClick(_:)), forControlEvents: .TouchUpInside)
        self.view.addSubview(fisrtBtn)
        self.view.addSubview(secondLabel)
    }

    func fisrtBtnClick(sender:UIButton)
    {
        let secondVc = SecondViewController()
        //實作回調，接收回調過來的值
        secondVc.setBackMyClosure { (inputText:String) in
            self.secondLabel.text = inputText
        }
        
    }
}
           

Second控制器:

typealias InputClosureType = (String)->Void   //閉包類型的函數 參數為string 傳回值void

class SecondViewController: UIViewController {

    var backBtn:UIButton = {
        let button:UIButton = UIButton()
        button.backgroundColor = UIColor.redColor()
        button.setTitle("back", forState: .Normal)
        button.layer.masksToBounds = true
        return button
    }()
    var backClosure:InputClosureType?        //聲明閉包函數
    override func viewDidLoad() {
        super.viewDidLoad()
        backBtn.frame = CGRectMake(100, 100, 100, 100)
        backBtn.addTarget(self, action: #selector(SecondViewController.tapBackButton(_:)), forControlEvents:.TouchUpOutside)
        self.view.addSubview(backBtn)
    }
    //閉包變量指派
    func setBackMyClosure(tempClosure:InputClosureType)
    {
        backClosure = tempClosure
    }
    
    func tapBackButton(sender:UIButton)
    {
        if(backClosure != nil)
        {
            let tempString:String? = "peng xun xun"
            if(tempString != nil)
            {
                backClosure!(tempString!)  //執行閉包
            }
        }
        self.navigationController?.popViewControllerAnimated(true)
    }

}
           

這就是閉包傳值基本上跟OC block的使用差不多如果你很熟悉的話那就很好了解，總的來說要使用一個閉合函數 得有

函數的參數與傳回值、函數體以及函數的執行。