swift中闭包的使用

swift中的闭包跟OC中的Block原理相似
本文用一个小Demo来展示具体用法
首先自定义了一个view，然后定义闭包，最后在viewcontroller中创建view并使用闭包传值

自定义view的代码：

import UIKit

//typealias IndexBlock  = (index:NSInteger)->Void

class CustomView: UIView {
    
    var IndexBlock:((index:NSInteger)->()) = {_ in }

    /*
    // Only override drawRect: if you perform custom drawing.
    // An empty implementation adversely affects performance during animation.
    override func drawRect(rect: CGRect) {
        // Drawing code
    }
    */
    
//    var callBack:IndexBlock!
    
    var button1:UIButton?
    var button2:UIButton?
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        
        setupUI()
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    func setupUI() {
        
        self.button1 = UIButton.init(type: .Custom)
        self.button1?.backgroundColor = UIColor.redColor()
        self.button1?.frame = CGRectMake(0, 65, 60, 30)
        self.button1?.tag = 1
        self.button1?.addTarget(self, action: #selector(buttonClick), forControlEvents: .TouchUpInside)
        self.addSubview(self.button1!)
        
        self.button2 = UIButton.init(type: .Custom)
        self.button2?.backgroundColor = UIColor.blueColor()
        self.button2?.frame = CGRectMake(0, 100, 60, 30)
        self.button2?.tag = 2
        self.button2?.addTarget(self, action: #selector(buttonClick), forControlEvents: .TouchUpInside)
        self.addSubview(self.button2!)
        
    }
    
    func buttonClick(sender:UIButton){
        
//        self.callBack!(index: sender.tag)
        self.IndexBlock(index: sender.tag)
    }
    

}

viewcontroller中的代码：

import UIKit

class ViewController: UIViewController {

    var cv:CustomView?
    
    var label:UILabel!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        
        configViews()
        
        
    }
    
    func configViews() {
        
        self.title = "首页"
        
        self.view.backgroundColor = UIColor.whiteColor()
        
        setupData()
        
        
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

}

extension ViewController {
    
    func setupData(){
        self.cv = CustomView.init(frame: CGRectMake(10, 10, 300, 300))
        self.cv!.backgroundColor = UIColor.yellowColor()
        self.view.addSubview(self.cv!)
        
        self.label = UILabel.init(frame: CGRectMake(10, 360, 200, 30))
        self.label.backgroundColor = UIColor.redColor()
        self.view.addSubview(self.label)
        
        /*
        self.cv?.callBack = {(index:NSInteger)->() in
            self.label.text = String(index)
            }
            */
        self.cv?.IndexBlock = {(index:NSInteger)->() in
            self.label.text = String(index)

            }
 
        }
    
}

代码中闭包用了两种写法，一种是常规写法，一种使用了typealias
不过我注释掉了其中一种写法，两种实现效果是一样的，可以根据自己的习惯去选择哪种写法