樂在其中設計模式(C#) - 裝飾模式(Decorator Pattern)
介紹
動态地給一個對象添加一些額外的職責。就擴充功能而言,它比生成子類方式更為靈活。
示例
有一個Message實體類,某個對象對它的操作有Insert()和Get()方法,現在擴充這個對象的功能。
MessageModel
using System;
using System.Collections.Generic;
using System.Text;
namespace Pattern.Decorator
{
/**//// <summary>
/// Message實體類
/// </summary>
public class MessageModel
/**//// <summary>
/// 構造函數
/// </summary>
/// <param name="msg">Message内容</param>
/// <param name="pt">Message釋出時間</param>
public MessageModel(string msg, DateTime pt)
this._message = msg;
this._publishTime = pt;
}
private string _message;
/// Message内容
public string Message
get
{ return _message; }
set
{ _message = value; }
private DateTime _publishTime;
/// Message釋出時間
public DateTime PublishTime
{ return _publishTime; }
{ _publishTime = value; }
}
}
AbstractMessage
/// 操作Message的抽象構件(Component)
public abstract class AbstractMessage
/// 擷取Message
/// <returns></returns>
public abstract List<MessageModel> Get();
/// 插入Message
/// <param name="mm">Message實體對象</param>
public abstract bool Insert(MessageModel mm);
SqlMessage
/// Sql方式操作Message(ConcreteComponent)
public class SqlMessage : AbstractMessage
public override List<MessageModel> Get()
List<MessageModel> l = new List<MessageModel>();
l.Add(new MessageModel("SQL方式擷取Message", DateTime.Now));
return l;
public override bool Insert(MessageModel mm)
// 代碼略
return true;
XmlMessage
/// Xml方式操作Message(ConcreteComponent)
public class XmlMessage : AbstractMessage
l.Add(new MessageModel("XML方式擷取Message", DateTime.Now));
AbstractMessageWrapper
/// 裝飾AbstractMessage(Decorator)
public abstract class AbstractMessageWrapper : AbstractMessage
private AbstractMessage _abstractMessage;
/// <param name="abstractMessage">AbstractMessage</param>
public AbstractMessageWrapper(AbstractMessage abstractMessage)
this._abstractMessage = abstractMessage;
return _abstractMessage.Get();
return _abstractMessage.Insert(mm);
CheckUserWrapper
/// 擴充出使用者驗證的功能(ConcreteDecorator)
public class CheckUserWrapper : AbstractMessageWrapper
public CheckUserWrapper(AbstractMessage abstractMessage)
: base(abstractMessage)
List<MessageModel> l = base.Get();
foreach (MessageModel mm in l)
mm.Message += "(經過使用者驗證)";
}
// 在這裡擴充功能
return base.Insert(mm);
CheckInputWrapper
/// 擴充出輸入驗證的功能(ConcreteDecorator)
public class CheckInputWrapper : AbstractMessageWrapper
public CheckInputWrapper(AbstractMessage abstractMessage)
mm.Message += "(經過輸入驗證)";
Test
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.Decorator;
public partial class Decorator : System.Web.UI.Page
protected void Page_Load(object sender, EventArgs e)
AbstractMessage message = new SqlMessage();
AbstractMessageWrapper amr = new CheckUserWrapper(message);
Response.Write(amr.Get()[0].Message + " " + amr.Get()[0].PublishTime.ToString());
Response.Write("<br />");
AbstractMessageWrapper amr2 = new CheckInputWrapper(message);
Response.Write(amr2.Get()[0].Message + " " + amr2.Get()[0].PublishTime.ToString());
AbstractMessageWrapper amr3 = new CheckUserWrapper(message);
AbstractMessageWrapper amr4 = new CheckInputWrapper(amr3);
Response.Write(amr4.Get()[0].Message + " " + amr4.Get()[0].PublishTime.ToString());
運作結果
SQL方式擷取Message(經過使用者驗證) 2007-5-13 19:34:01
SQL方式擷取Message(經過輸入驗證) 2007-5-13 19:34:01
SQL方式擷取Message(經過使用者驗證)(經過輸入驗證) 2007-5-13 19:34:01
參考
<a href="http://www.dofactory.com/Patterns/PatternDecorator.aspx" target="_blank">http://www.dofactory.com/Patterns/PatternDecorator.aspx</a>
OK
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