设计模式之代理模式

理解如下:

1. 客户端不能直接调用具体的业务类时可以使用代理类.
2. 代理类和业务类重同一接口继承下来.
3. 代理类调用业务类,客户端调用代理类.

接口代码:

 /// <summary>
    /// 定义客户端调用的目标对象的接口
    /// </summary>
    public interface IPlayMusic
    {
        string PlayMusic(string musicType);
    }

 业务类代码:

public class PlaySubject:IPlayMusic
    {
        private static readonly PlaySubject instance = new PlaySubject();

        private PlaySubject()
        { 
            
        }

        public static IPlayMusic PlaySuject
        {
            get
            {
                return instance;
            }
        }
        
        #region IPlayMusic 成员

        public string PlayMusic(string musicType)
        {
            if (musicType == "mp3")
            {
                return "mp3";
            }
            else
            {
                return "other";
            }
        }

        #endregion
    }

代理类代码:

 public class PlayMusicProxy:IPlayMusic
    {
        #region IPlayMusic 成员

        public string PlayMusic(string musicType)
        {
            return PlaySubject.PlaySuject.PlayMusic(musicType);
        }

        #endregion
    }

客户段代码:

 PlayMusicProxy proxy = new PlayMusicProxy();
            string str;
            str = proxy.PlayMusic("mp3");
            Response.Write(str); 

问题:

看来看去好象作用不大,好处是什么?代理类封装了业务逻辑,简化了客户端代码?