在iOS开发中，如果创建一个自定义的组件通常可以通过继承UIView来实现。下面以一个记分牌组件为例，演示了组件的创建和使用，以及枚举、协议等相关知识的学习。（本文代码已升级至Swift3）

import UIKit

enum ScoreType{
    case common  //普通分数面板
    case best    //最高分面板
}

protocol ScoreViewProtocol{
    
    func changeScore(value s:Int)
}

class ScoreView:UIView, ScoreViewProtocol
{
    var label:UILabel!
    
    let defaultFrame = CGRect(x:0, y:0, width:100, height:30)
    var stype:String!  //显示”最高分“还是”分数“
    var score:Int = 0{
        didSet{
            //分数变化，标签内容也要变化
            label.text = "\(stype!):\(score)"
        }
    }
    
    //传入分数面板的类型，用于控制标签的显示
    init(stype:ScoreType)
    {
        label = UILabel(frame:defaultFrame)
        label.textAlignment = .center
        
        super.init(frame:defaultFrame)
        
        self.stype = (stype == .common ? "分数":"最高分")
        
        backgroundColor = UIColor.orange
        label.font = UIFont(name:"微软雅黑", size:16)
        label.textColor = UIColor.white
        self.addSubview(label)
    }
    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }
    
    //实现协议中的方法
    func changeScore(value s:Int)
    {
        score = s
    }
}

组件使用：

import UIKit

class ViewController: UIViewController {
    
    var score:ScoreView!
    var bestscore:ScoreView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        setupScoreLabels();
    }
    
    func setupScoreLabels()
    {
        score = ScoreView(stype: .common)
        score.frame.origin = CGPoint(x:50, y:80)
        score.changeScore(value: 0)
        self.view.addSubview(score)
        
        bestscore = ScoreView(stype: .best)
        bestscore.frame.origin.x = 170
        bestscore.frame.origin.y = 80
        bestscore.changeScore(value: 99)
        self.view.addSubview(bestscore)
    }
    
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
}