乐在其中设计模式(C#) - 命令模式(Command Pattern)

2022-10-28 21:31:27

作者：webabcd

介绍

将一个请求封装为一个对象，从而使你可用不同的请求对客户进行参数化；对请求排队或记录请求日志，以及支持可取消的操作。

示例

有一个Message实体类，某个类对它的操作有Insert()和Delete()方法。现在要求可以对之前的所有操作做撤销和重复。

MessageModel

using System;

using System.Collections.Generic;

using System.Text;

namespace Pattern.Command

{

/**//// <summary>

/// Message实体类

/// </summary>

public class MessageModel

{

/**//// <summary>

/// 构造函数

/// </summary>

/// <param name="msg">Message内容</param>

/// <param name="pt">Message发布时间</param>

public MessageModel(string msg, DateTime pt)

{

this._message = msg;

this._publishTime = pt;

}

private string _message;

/**//// <summary>

/// Message内容

/// </summary>

public string Message

{

get

{ return _message; }

set

{ _message = value; }

}

private DateTime _publishTime;

/**//// <summary>

/// Message发布时间

/// </summary>

public DateTime PublishTime

{

get

{ return _publishTime; }

set

{ _publishTime = value; }

}

Action

using System;

using System.Collections.Generic;

using System.Text;

namespace Pattern.Command

{

/**//// <summary>

/// enum

/// 定义操作的两种方法Insert和Delete

/// </summary>

public enum Action

{

/**//// <summary>

/// Insert

/// </summary>

Insert,

/**//// <summary>

/// Delete

/// </summary>

Delete

}

SqlMessage

using System;

using System.Collections.Generic;

using System.Text;

namespace Pattern.Command

{

/**//// <summary>

/// 接收者（Receiver）角色

/// Sql方式操作Message

/// </summary>

public class SqlMessage

{

/**//// <summary>

/// 操作

/// </summary>

/// <param name="action">操作的方法</param>

/// <param name="mm">Message实体对象</param>

public void Operation(Action action, MessageModel mm)

{

switch (action)

{

case Action.Insert :

Insert(mm);

break;

case Action.Delete :

Delete(mm);

break;

}

/**//// <summary>

/// 插入Message

/// </summary>

/// <param name="mm">Message实体对象</param>

private void Insert(MessageModel mm)

{

// 代码略

}

/**//// <summary>

/// 删除Message

/// </summary>

/// <param name="mm">Message实体对象</param>

private void Delete(MessageModel mm)

{

// 代码略

}

ICommand

using System;

using System.Collections.Generic;

using System.Text;

namespace Pattern.Command

{

/**//// <summary>

/// 命令（Command）角色

/// </summary>

public interface ICommand

{

/**//// <summary>

/// 执行

/// </summary>

/// <returns>操作的方法及操作的信息</returns>

string Execute();

/**//// <summary>

/// 取消执行

/// </summary>

/// <returns>操作的方法及操作的信息</returns>

string UnExecute();

}

SqlMessageCommand

using System;

using System.Collections.Generic;

using System.Text;

namespace Pattern.Command

{

/**//// <summary>

/// 具体命令（ConcreteCommand）角色

/// </summary>

public class SqlMessageCommand : ICommand

{

/**//// <summary>

/// 操作的方法

/// </summary>

private Action _action;

/**//// <summary>

/// Message实体对象

/// </summary>

private MessageModel _mm;

/**//// <summary>

/// 构造函数

/// </summary>

/// <param name="action">操作的方法</param>

/// <param name="mm">Message实体对象</param>

public SqlMessageCommand(Action action, MessageModel mm)

{

this._action = action;

this._mm = mm;

}

/**//// <summary>

/// 执行

/// </summary>

/// <returns>操作的方法及操作的信息</returns>

public string Execute()

{

new SqlMessage().Operation(_action, _mm);

return _action.ToString() + "：" + _mm.Message;

}

/**//// <summary>

/// 取消执行（调用一个方法，以决定取消执行的算法）

/// </summary>

/// <returns>操作的方法及操作的信息</returns>

public string UnExecute()

{

_action = GetUndoAction(_action);

new SqlMessage().Operation(_action, _mm);

return _action.ToString() + "：" + _mm.Message;

}

/**//// <summary>

/// 获得取消执行的算法

/// </summary>

/// <param name="action">操作的方法</param>

/// <returns></returns>

private Action GetUndoAction(Action action)

{

Action undo;

switch (action)

{

case Action.Insert :

undo = Action.Delete;

break;

case Action.Delete :

undo = Action.Insert;

break;

// 这句没啥用

default :

undo = Action.Insert;

break;

}

return undo;

}

Message

using System;

using System.Collections.Generic;

using System.Text;

namespace Pattern.Command

{

/**//// <summary>

/// 请求者（Invoker）角色

/// </summary>

public class Message

{

/**//// <summary>

/// 命令集合（保存每次操作）

/// </summary>

private List<ICommand> _listCommand = new List<ICommand>();

/**//// <summary>

/// 命令集合中当前要执行的命令的索引

/// </summary>

;

/**//// <summary>

/// 执行Sql

/// </summary>

/// <param name="action">操作的方法</param>

/// <param name="mm">Message实体对象</param>

/// <returns>操作的方法及操作的信息</returns>

public string Do(Action action, MessageModel mm)

{

string rtn = "";

ICommand cmd = new SqlMessageCommand(action, mm);

rtn = cmd.Execute();

_listCommand.Add(cmd);

current++;

return rtn;

}

/**//// <summary>

/// 撤销

/// </summary>

/// <param name="levels">执行撤销操作的次数</param>

/// <returns>操作的方法及操作的信息（用空格分开多条记录）</returns>

public string Undo(int levels)

{

string rtn = "";

; i < levels; i++)

{

)

{

ICommand cmd = _listCommand[--current];

rtn += cmd.UnExecute() + " ";

}

return rtn;

}

/**//// <summary>

/// 重复

/// </summary>

/// <param name="levels">执行重复操作的次数</param>

/// <returns>操作的方法及操作的信息（用空格分开多条记录）</returns>

public string Redo(int levels)

{

string rtn = "";

; i < levels; i++)

{

)

{

ICommand cmd = _listCommand[current++];

rtn += cmd.UnExecute() + " ";

}

return rtn;

}

client

using System;

using System.Data;

using System.Configuration;

using System.Collections;

using System.Web;

using System.Web.Security;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.Web.UI.WebControls.WebParts;

using System.Web.UI.HtmlControls;

using Pattern.Command;

public partial class Command : System.Web.UI.Page

{

protected void Page_Load(object sender, EventArgs e)

{

Message m = new Message();

Response.Write("操作");

Response.Write(" ");

Response.Write(m.Do(Action.Insert, new MessageModel("第1条", DateTime.Now)));

Response.Write(" ");

Response.Write(m.Do(Action.Insert, new MessageModel("第2条", DateTime.Now)));

Response.Write(" ");

Response.Write(m.Do(Action.Insert, new MessageModel("第3条", DateTime.Now)));

Response.Write(" ");

Response.Write(m.Do(Action.Insert, new MessageModel("第4条", DateTime.Now)));

Response.Write(" ");

Response.Write(m.Do(Action.Delete, new MessageModel("第2条", DateTime.Now)));

Response.Write(" ");

Response.Write(m.Do(Action.Insert, new MessageModel("第5条", DateTime.Now)));

Response.Write(" ");

Response.Write(m.Do(Action.Delete, new MessageModel("第3条", DateTime.Now)));

Response.Write(" ");

Response.Write(m.Do(Action.Insert, new MessageModel("第6条", DateTime.Now)));

Response.Write(" ");

Response.Write(m.Do(Action.Insert, new MessageModel("第7条", DateTime.Now)));

Response.Write(" ");

Response.Write("撤销4次操作");

Response.Write(" ");

Response.Write(m.Undo());

Response.Write(" ");

Response.Write("重复2次操作");

Response.Write(" ");

Response.Write(m.Redo());

Response.Write(" ");

Response.Write("撤销3次操作");

Response.Write(" ");

Response.Write(m.Undo());

}

运行结果

操作

Insert：第1条

Insert：第2条

Insert：第3条

Insert：第4条

Delete：第2条

Insert：第5条

Delete：第3条

Insert：第6条

Insert：第7条

撤销4次操作

Delete：第7条 Delete：第6条 Insert：第3条 Delete：第5条

重复2次操作

Insert：第5条 Delete：第3条

撤销3次操作

Insert：第3条 Delete：第5条 Insert：第2条

参考

http://www.dofactory.com/Patterns/PatternCommand.aspx

OK

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