（Target-Action,协议，闭包）

简单控件用闭包

复杂控件用协议

新建一个类ProtocolSlider
//协议的优点：明确
//协议的缺点：复杂，步骤太多
//如果有optional方法，必须使用@objc

@objc protocol ProtocolSliderDelegate {

    optional func didChange(slider: ProtocolSlider类名)

}

class ProtocolSlider: UIView {

    let trackView = UIView()      

    

//    用于关联两个对象(控件与需要获取事件的对象)

    var delegate: ProtocolSliderDelegate!

//    如果使用闭包，定义一个闭包

//    var didChange: ((ProtocolSlider) -> Void)!

    var minValue: CGFloat = 0

    var maxValue: CGFloat = 1

    

    var currentValue: CGFloat = 0.5 {

        didSet {

            //            self.sendActionsForControlEvents(.ValueChanged)

            

            self.setNeedsLayout()

        }

    }

    

    override init(frame: CGRect) {

        super.init(frame: frame)

        

        self.addSubview(trackView)

        

        self.backgroundColor = UIColor.cyanColor()

        trackView.backgroundColor = UIColor.redColor()

    }

    

    required init?(coder aDecoder: NSCoder) {

        super.init(coder: aDecoder)

        

        self.addSubview(trackView)

        

        self.backgroundColor = UIColor.cyanColor()

        trackView.backgroundColor = UIColor.redColor()

    }

    

    func moveTrack(touches: NSSet) {

        let touch = touches.anyObject() as! UITouch

        

        let location = touch.locationInView(self)

        currentValue = (location.x / self.frame.size.width) * (maxValue - minValue) +minValue

    }

    

    //开始触摸

    override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {

        //        print("begin")

        

        moveTrack(touches)

    }

    

    //移动

    override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent?) {

        //        print("continue")

        

        moveTrack(touches)

    }

    

    override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent?) {

        //        print("end")

        

        //触发事件

//        self.sendActionsForControlEvents(.ValueChanged)

//        实现闭包

//        1. 如果使用协议，需要确保delegate是否为空

//        2. 如果方法为optional，需要确保方法是否实现

//        if delegate != nil {

//            if delegate.didChange != nil {

//                delegate.didChange!(self)

//            }

//        }

        

        if didChange != nil {

            didChange(self)

        }

    }

    

    override func layoutSubviews() {

        super.layoutSubviews()

        

        let width = (currentValue - minValue) * self.frame.size.width / (maxValue -minValue)

        let rect = CGRect(x: 0, y: 0, width: width, height: self.frame.size.height)

        trackView.frame = rect

    }

}

在ViewControl中实现协议

import UIKit

class ViewController: UIViewController, ProtocolSliderDelegate, UITableViewDelegate {

    override func viewDidLoad() {

        super.viewDidLoad()

        

        //UIControl

        //Target-Action

        

        let slider = ProtocolSlider(frame: CGRect(x: 100, y: 100, width: 200, height:50))

//    UIControl    addTarget  实现方法   

//        slider.addTarget(self, action: #selector(didChange(_:)), forControlEvents: .ValueChanged)

//        slider.delegate = self

        

//        调用闭包

//        slider.didChange = {

//            sender in

//            print(sender.currentValue)

//        }

        

        //函数：特殊闭包

        //闭包：匿名函数

        slider.didChange = didChange          协议实现方法   

        self.view.addSubview(slider)          协议实现方法   

    }

    func didChange(sender: ProtocolSlider) {
        print(sender.currentValue)
    }
}