《Head First Design Patterns》笔记十五：MVC

 概述

    MVC是很流行的一种模式。不过并不是GOF定义的23种标准模式之一，我们可以称呼它为一种框架，其实本质就是一种特定的复合模式。

我们分析下MVC

 

    界面Viewer-controller， controller-model都是使用的策略模式。这样使得3者松耦合，可以灵活选择其他策略，我们想像下，是不是有不少厂商，把旗下电器，换个外壳，改个名字，照样拿出来卖的啊，有没有，有，他们就是换了个viewer来榨取最大利润。

   ok，里面还有观察者模式，当model状态改变的时候，往往需要通知viewer 和controller.比如控制model的温度上升，那么viewer面板上如果需要知道温度状况的时候，就需要订阅model的温度改变事件了,controller需要了解情况的时候，同样订阅事件。

   那么，我们可以说策略模式+观察者模式=MVC，ok，基本的MVC的确是这样。当然实际MVC应用会更加复杂。不过也只是更多的扩展罢了。

实例

    闲话休说，还是来点直观的例子吧。我们现在要做一个播放器，要有播放/停止，音量增加/减小，上一首/下一首歌切换功能。

好，那播放界面就是viewer，contoller控制音量增加/减小，播放/停止，等具体操作，实际数据都在model，

   1 首先实现Model，

    接口IModdel.cs:

  using System;namespace FUZHEPING.DesignPatterns.MVC{public delegate void StatusSetHandler(bool isPlay);public delegate void VolumnSetHandler(int volumn);public delegate void SongIDSetHandler(int id);public interface IModel{event StatusSetHandler OnStatusSet;event VolumnSetHandler OnVolumnSet;event SongIDSetHandler OnSongIDSet;int Volumn{get;set;}int SongID{get;set;}bool Play{get;set;}}}

  实际model实现SongModel.cs:

 using System;namespace FUZHEPING.DesignPatterns.MVC{public class SongModel:IModel{public event StatusSetHandler OnStatusSet;public event VolumnSetHandler OnVolumnSet;public event SongIDSetHandler OnSongIDSet;int _volumn;public int Volumn{get{return _volumn;}set{ _volumn=value; if (OnVolumnSet!=null) OnVolumnSet(value);}}int _songID;public int SongID{get{return _songID;}set{_songID=value;if (OnSongIDSet!=null) OnSongIDSet(value);}}bool _play;public bool Play{get{return _play;}set {_play=value;if (OnStatusSet!=null) OnStatusSet(value);}}}}

2.实现Controller

  IController.cs.如下

 using System;namespace FUZHEPING.DesignPatterns.MVC{public interface IController{void VolumnUp();void VolumnDown();void NextSong();void PreviousSong();void Play();void Stop();}}

 SongController.cs:

using System;namespace FUZHEPING.DesignPatterns.MVC{public class SongController:IController{IModel _songModel;public SongController(IModel model){_songModel=model;}int maxSong=100;int maxVolumn=100;public void VolumnUp(){if (_songModel.Volumn<maxVolumn) _songModel.Volumn++;}public void VolumnDown(){if (_songModel.Volumn>0) _songModel.Volumn--;}public void NextSong(){_songModel.SongID=_songModel.SongID % maxSong+1;}public void PreviousSong(){_songModel.SongID=(_songModel.SongID-2+maxSong) % maxSong+1;}public void Play(){_songModel.Play=true;}public void Stop(){_songModel.Play=false;}}}

3,接着就是实现界面Viewer.cs

using System;using System.Drawing;using System.Windows.Forms;namespace FUZHEPING.DesignPatterns.MVC{class Viewer:Form{IController controller;bool isPlay=false;#region UI ControlsRichTextBox rt_info=new RichTextBox();Button btn_Previous=new Button();Button btn_Next=new Button();Button btn_VolUp=new Button();Button btn_VolDown=new Button();Button btn_Run=new Button();#endregionpublic Viewer(IController controller){InitialComponent();this.controller=controller;}void InitialComponent(){this.Size=new Size(440,190);rt_info.Size=new Size(90,90);rt_info.Dock=DockStyle.Top;this.Controls.Add(rt_info);btn_Previous.Text="Previous song";btn_Previous.Location=new Point(0,100);btn_Previous.Size=new Size(100,23);btn_Previous.Click+=btn_Previous_OnClick;this.Controls.Add(btn_Previous);btn_Next.Text="Next song";btn_Next.Location=new Point(110,100);btn_Next.Size=new Size(90,23);btn_Next.Click+=btn_Next_OnClick;this.Controls.Add(btn_Next);btn_VolUp.Text="Volumn Up";btn_VolUp.Location=new Point(220,100);btn_VolUp.Size=new Size(90,23);btn_VolUp.Click+=btn_VolUp_OnClick;this.Controls.Add(btn_VolUp);btn_VolDown.Text="Volumn Down";btn_VolDown.Location=new Point(330,100);btn_VolDown.Size=new Size(90,23);btn_VolDown.Click+=btn_VolDown_OnClick;this.Controls.Add(btn_VolDown);SetPlayButtonTitle();btn_Run.Location=new Point(0,130);btn_Run.Click+=btn_Run_OnClick;this.Controls.Add(btn_Run);}public void ShowSongID(int id){rt_info.AppendText(string.Format("now is playing song {0}/n",id));}public void ShowVolumn(int volumn){rt_info.AppendText(string.Format("the volumn is {0}/n",volumn));}public void ShowPlayStatus(bool play){isPlay=play;SetPlayButtonTitle();rt_info.AppendText(string.Format("music is {0}/n",play?"play":"stop" ));}void btn_Previous_OnClick(object sender,EventArgs args){controller.PreviousSong();}void btn_Next_OnClick(object sender,EventArgs args){controller.NextSong();}void btn_VolUp_OnClick(object sender,EventArgs args){controller.VolumnUp();}void btn_VolDown_OnClick(object sender ,EventArgs args){controller.VolumnDown();}void btn_Run_OnClick(object sender,EventArgs args){ if (isPlay) controller.Stop(); else controller.Play();}void SetPlayButtonTitle(){btn_Run.Text=(isPlay)?"Stop":"Play";}}}

4:运行实例了Program.cs如下：

using System;using System.Windows.Forms;namespace FUZHEPING.DesignPatterns.MVC{public class Program{public static void Main(){IModel model=new SongModel();IController controller=new SongController(model);Viewer v=new Viewer(controller);model.OnStatusSet+=v.ShowPlayStatus;model.OnVolumnSet+=v.ShowVolumn;model.OnSongIDSet+=v.ShowSongID;Application.Run(v);}}}

 运行结果：

 

如上图，用户可以点按钮控制播放器了，播放信息出现在RichText框内

是不是感觉界面比较粗糙啊，汗，只是个范例。简单最好，哈哈。

 

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