原文:
乐在其中设计模式(C#) - 观察者模式(Observer Pattern)
作者： webabcd
介绍
定义对象间的一种一对多的依赖关系,以便当一个对象的状态发生改变时,所有依赖于它的对象都得到通知并自动刷新。
示例
有一个Message实体类，某些对象对它的操作有Insert()方法，当发生某些改变的时候，通知所有这些对象并执行Insert()方法。
MessageModel
using
System;
using
System.Collections.Generic;
using
System.Text;
namespace
Pattern.Observer
{
/// <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; }
}
}
}
IMessage
using
System;
using
System.Collections.Generic;
using
System.Text;
namespace
Pattern.Observer
{
/// <summary>
/// 操作Message的接口（Observer）
/// </summary>
public interface IMessage
{
/// <summary>
/// 插入Message
/// </summary>
/// <param name="mm">Message实体对象</param>
/// <returns></returns>
string Insert(MessageModel mm);
}
}
SqlMessage
using
System;
using
System.Collections.Generic;
using
System.Text;
namespace
Pattern.Observer
{
/// <summary>
/// Sql方式操作Message（ConcreteObserver）
/// </summary>
public class SqlMessage : IMessage
{
/// <summary>
/// 插入Message
/// </summary>
/// <param name="mm">Message实体对象</param>
/// <returns></returns>
public string Insert(MessageModel mm)
{
return "sql方式：" + mm.Message + " " + mm.PublishTime.ToString();
}
}
}
XmlMessage
using
System;
using
System.Collections.Generic;
using
System.Text;
namespace
Pattern.Observer
{
/// <summary>
/// Xml方式操作Message（ConcreteObserver）
/// </summary>
public class XmlMessage : IMessage
{
/// <summary>
/// 插入Message
/// </summary>
/// <param name="mm">Message实体对象</param>
/// <returns></returns>
public string Insert(MessageModel mm)
{
return "xml方式：" + mm.Message + " " + mm.PublishTime.ToString();
}
}
}
AbstractMessageSubject
using
System;
using
System.Collections.Generic;
using
System.Text;
namespace
Pattern.Observer
{
/// <summary>
/// 抽象Message主题（Subject）
/// </summary>
public abstract class AbstractMessageSubject
{
private MessageModel _messageModel;
private List<IMessage> list = new List<IMessage>();
/// <summary>
/// 构造函数
/// </summary>
/// <param name="mm">Message实体对象</param>
public AbstractMessageSubject(MessageModel mm)
{
this._messageModel = mm;
}
/// <summary>
/// 添加一个实现IMessage接口的对象
/// </summary>
/// <param name="m">实现IMessage接口的对象</param>
public void Attach(IMessage m)
{
list.Add(m);
}
/// <summary>
/// 移除一个实现IMessage接口的对象
/// </summary>
/// <param name="m">实现IMessage接口的对象</param>
public void Detach(IMessage m)
{
list.Remove(m);
}
/// <summary>
/// 通知所有观察者
/// </summary>
/// <returns></returns>
public string Notify()
{
string s = "";
foreach (IMessage i in list)
{
s += i.Insert(_messageModel);
s += "<br />";
}
return s;
}
/// <summary>
/// Message发布时间
/// </summary>
public DateTime PublishTime
{
get { return _messageModel.PublishTime; }
set
{
_messageModel.PublishTime = value;
Notify();
}
}
}
}
MessageSubject
using
System;
using
System.Collections.Generic;
using
System.Text;
namespace
Pattern.Observer
{
/// <summary>
/// Message主题（ConcreteSubject）
/// </summary>
public class MessageSubject : AbstractMessageSubject
{
/// <summary>
/// 构造函数
/// </summary>
/// <param name="mm">Message实体对象</param>
public MessageSubject(MessageModel mm)
: base(mm)
{
}
}
}
Test
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.Observer;
public
partial
class
Observer : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
MessageSubject m = new MessageSubject(new MessageModel("插入Message", DateTime.Now));
SqlMessage sqlMessage = new SqlMessage();
XmlMessage xmlMessage = new XmlMessage();
m.Attach(sqlMessage);
m.Attach(xmlMessage);
// System.Threading.Thread.Sleep(1000);
// 修改了PublishTime就会通知所有观察者
// m.PublishTime = DateTime.Now;
Response.Write(m.Notify());
}
}
运行结果
sql方式：插入Message 2007-5-26 9:38:18
xml方式：插入Message 2007-5-26 9:38:18
参考
http://www.dofactory.com/Patterns/PatternObserver.aspx
OK
[源码下载]
乐在其中设计模式(C#) - 观察者模式(Observer Pattern)
作者： webabcd
介绍
定义对象间的一种一对多的依赖关系,以便当一个对象的状态发生改变时,所有依赖于它的对象都得到通知并自动刷新。
示例
有一个Message实体类，某些对象对它的操作有Insert()方法，当发生某些改变的时候，通知所有这些对象并执行Insert()方法。
MessageModel
using
System;
using
System.Collections.Generic;
using
System.Text;
namespace
Pattern.Observer
{
/// <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; } } }}
IMessage
using
System;
using
System.Collections.Generic;
using
System.Text;
namespace
Pattern.Observer
{ /// <summary> /// 操作Message的接口（Observer） /// </summary> public interface IMessage { /// <summary> /// 插入Message /// </summary> /// <param name="mm">Message实体对象</param> /// <returns></returns> string Insert(MessageModel mm); }}
SqlMessage
using
System;
using
System.Collections.Generic;
using
System.Text;
namespace
Pattern.Observer
{ /// <summary> /// Sql方式操作Message（ConcreteObserver） /// </summary> public class SqlMessage : IMessage { /// <summary> /// 插入Message /// </summary> /// <param name="mm">Message实体对象</param> /// <returns></returns> public string Insert(MessageModel mm) { return "sql方式：" + mm.Message + " " + mm.PublishTime.ToString(); } }}
XmlMessage
using
System;
using
System.Collections.Generic;
using
System.Text;
namespace
Pattern.Observer
{ /// <summary> /// Xml方式操作Message（ConcreteObserver） /// </summary> public class XmlMessage : IMessage { /// <summary> /// 插入Message /// </summary> /// <param name="mm">Message实体对象</param> /// <returns></returns> public string Insert(MessageModel mm) { return "xml方式：" + mm.Message + " " + mm.PublishTime.ToString(); } }}
AbstractMessageSubject
using
System;
using
System.Collections.Generic;
using
System.Text;
namespace
Pattern.Observer
{ /// <summary> /// 抽象Message主题（Subject） /// </summary> public abstract class AbstractMessageSubject { private MessageModel _messageModel; private List<IMessage> list = new List<IMessage>(); /// <summary> /// 构造函数 /// </summary> /// <param name="mm">Message实体对象</param> public AbstractMessageSubject(MessageModel mm) { this._messageModel = mm; } /// <summary> /// 添加一个实现IMessage接口的对象 /// </summary> /// <param name="m">实现IMessage接口的对象</param> public void Attach(IMessage m) { list.Add(m); } /// <summary> /// 移除一个实现IMessage接口的对象 /// </summary> /// <param name="m">实现IMessage接口的对象</param> public void Detach(IMessage m) { list.Remove(m); } /// <summary> /// 通知所有观察者 /// </summary> /// <returns></returns> public string Notify() { string s = ""; foreach (IMessage i in list) { s += i.Insert(_messageModel); s += "<br />"; } return s; } /// <summary> /// Message发布时间 /// </summary> public DateTime PublishTime { get { return _messageModel.PublishTime; } set { _messageModel.PublishTime = value; Notify(); } } }}
MessageSubject
using
System;
using
System.Collections.Generic;
using
System.Text;
namespace
Pattern.Observer
{ /// <summary> /// Message主题（ConcreteSubject） /// </summary> public class MessageSubject : AbstractMessageSubject { /// <summary> /// 构造函数 /// </summary> /// <param name="mm">Message实体对象</param> public MessageSubject(MessageModel mm) : base(mm) { } }}
Test
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.Observer;
public
partial
class
Observer : System.Web.UI.Page
{ protected void Page_Load(object sender, EventArgs e) { MessageSubject m = new MessageSubject(new MessageModel("插入Message", DateTime.Now)); SqlMessage sqlMessage = new SqlMessage(); XmlMessage xmlMessage = new XmlMessage(); m.Attach(sqlMessage); m.Attach(xmlMessage); // System.Threading.Thread.Sleep(1000); // 修改了PublishTime就会通知所有观察者 // m.PublishTime = DateTime.Now; Response.Write(m.Notify()); }}
运行结果
sql方式：插入Message 2007-5-26 9:38:18
xml方式：插入Message 2007-5-26 9:38:18
参考
http://www.dofactory.com/Patterns/PatternObserver.aspx
OK
[源码下载]
