C#设计模式--观察者模式(发布-订阅模式)

0.C#设计模式–简单工厂模式

1.C#设计模式–工厂方法模式

2.C#设计模式–抽象工厂模式

3.C#设计模式–单例模式

4.C#设计模式–建造者模式

5.C#设计模式–原型模式

6.C#设计模式–设配器模式

7.C#设计模式–装饰器模式

8.C#设计模式–代理模式

9.C#设计模式–外观模式

10.C#设计模式–桥接模式

设计模式:

观察者模式(Observer Pattern)

简单介绍:

  观察者模式(Observer Pattern)是设计模式中行为模式的一种,它解决了上述具有一对多依赖关系的对象的重用问题。此模式的参与者分为两大类,一类是被观察的目标,另一类是观察该目标的观察者们。正因为该模式是基于“一对多”的关系,所以该模式一般是应用于由一个目标对象和N个观察者对象组成(当然也可以扩展为有多个目标对象,但我们现在只讨论前者)的场合。当目标对象的状态发生改变或做出某种行为时,正在观察该目标对象的观察者们将自动地、连锁地作出相应的响应行为。

模式中具有的角色

  1. 抽象主题(Subject):它把所有观察者对象的引用保存到一个聚集里,每个主题都可以有任何数量的观察者。抽象主题提供一个接口,可以增加和删除观察者对象。
  2. 具体主题(ConcreteSubject):将有关状态存入具体观察者对象;在具体主题内部状态改变时,给所有登记过的观察者发出通知。
  3. 抽象观察者(Observer):为所有的具体观察者定义一个接口,在得到主题通知时更新自己。
  4. 具体观察者(ConcreteObserver):实现抽象观察者角色所要求的更新接口,以便使本身的状态与主题状态协调。

举例子:博客的例子就是一个观察者模式,比如你关注一些作者的博客,当作者有博客发布时候,你就会收到一条该作者发布的博客的消息。

抽象主题:Blog 博客

具体主题:MyBlog   的博客

抽象观察者:IObserver  

具体的观察者:Observer

观察者模式类图:

《C#设计模式--观察者模式(发布-订阅模式)》

观察者模式C#代码举例

订阅博客抽象类

 1 /*****************************************************
 2  * ProjectName:  _11DesignPattern_Observer
 3  * Description:
 4  * ClassName:    Blog
 5  * CLRVersion:   4.0.30319.18408
 6  * Author:       JiYF
 7  * NameSpace:    _11DesignPattern_Observer
 8  * MachineName:  JIYONGFEI
 9  * CreateTime:   2017/5/23 17:08:10
10  * UpdatedTime:  2017/5/23 17:08:10
11 *****************************************************/
12 using System;
13 using System.Collections.Generic;
14 using System.Linq;
15 using System.Text;
16 
17 namespace _11DesignPattern_Observer
18 {
19     /// <summary>
20     /// 订阅博客抽象类
21     /// </summary>
22     public abstract class Blog
23     {
24         /// <summary>
25         /// 保存订阅者列表
26         /// </summary>
27         private List<IObserver> observers = new List<IObserver>();
28 
29         /// <summary>
30         /// 博主名
31         /// </summary>
32         public string BlogName { get; set; }
33 
34         /// <summary>
35         /// 博客标题
36         /// </summary>
37         public string BlogTitle { get; set; } 
38 
39         /// <summary>
40         /// 博客信息
41         /// </summary>
42         public string BlogInfo { get; set; }
43 
44         /// <summary>
45         /// 博客构造函数
46         /// </summary>
47         /// <param name="blogTitle">博客标题</param>
48         /// <param name="blogInfo">博客信息</param>
49         public Blog(string name,string blogTitle,string blogInfo)
50         {
51             this.BlogName = name;
52             this.BlogTitle = blogTitle;
53             this.BlogInfo = blogInfo;
54         }
55 
56         /// <summary>
57         /// 添加一个订阅者
58         /// </summary>
59         /// <param name="observer">具体的订阅者对象</param>
60         public void AddObserver(IObserver observer)
61         {
62             if (observers.Contains(observer))
63             {
64                 return;
65             }
66             observers.Add(observer);
67         }
68 
69         /// <summary>
70         /// 删除一个订阅者
71         /// </summary>
72         /// <param name="observer">具体的订阅者对象</param>
73         public void RemoveObserver(IObserver observer)
74         {
75             if (observers.Contains(observer))
76             {
77                 observers.Remove(observer);
78             }
79         }
80 
81         /// <summary>
82         /// 发布博客通知
83         /// </summary>
84         public void PublishBlog()
85         {
86             //遍历通知每一个订阅者
87             foreach (IObserver ob in observers)
88             {
89                 if (ob != null)
90                 {
91                     ob.Receive(this);
92                 }
93             }
94         }
95 
96     }
97 }

具体的博客类

 1 /*****************************************************
 2  * ProjectName:  _11DesignPattern_Observer
 3  * Description:
 4  * ClassName:    JiYFBlog
 5  * CLRVersion:   4.0.30319.18408
 6  * Author:       JiYF
 7  * NameSpace:    _11DesignPattern_Observer
 8  * MachineName:  JIYONGFEI
 9  * CreateTime:   2017/5/23 17:21:23
10  * UpdatedTime:  2017/5/23 17:21:23
11 *****************************************************/
12 using System;
13 using System.Collections.Generic;
14 using System.Linq;
15 using System.Text;
16 
17 namespace _11DesignPattern_Observer
18 {
19 
20     /// <summary>
21     /// 具体的订阅博客类
22     /// </summary>
23     public class JiYFBlog :Blog
24     {
25         public JiYFBlog(string name,string blogTitile, string blogInfo)
26             : base(name,blogTitile,blogInfo)
27         {
28             
29         }
30     }
31 }

订阅者接口类

 1 /*****************************************************
 2  * ProjectName:  _11DesignPattern_Observer
 3  * Description:
 4  * ClassName:    IObserver
 5  * CLRVersion:   4.0.30319.18408
 6  * Author:       JiYF
 7  * NameSpace:    _11DesignPattern_Observer
 8  * MachineName:  JIYONGFEI
 9  * CreateTime:   2017/5/23 17:09:28
10  * UpdatedTime:  2017/5/23 17:09:28
11 *****************************************************/
12 using System;
13 using System.Collections.Generic;
14 using System.Linq;
15 using System.Text;
16 
17 namespace _11DesignPattern_Observer
18 {
19     /// <summary>
20     /// 订阅者接口
21     /// </summary>
22     public interface IObserver
23     {
24 
25         void Receive(Blog blog);
26     }
27 }

具体的订阅者类:

 1 /*****************************************************
 2  * ProjectName:  _11DesignPattern_Observer
 3  * Description:
 4  * ClassName:    Observer
 5  * CLRVersion:   4.0.30319.18408
 6  * Author:       JiYF
 7  * NameSpace:    _11DesignPattern_Observer
 8  * MachineName:  JIYONGFEI
 9  * CreateTime:   2017/5/23 17:23:36
10  * UpdatedTime:  2017/5/23 17:23:36
11 *****************************************************/
12 using System;
13 using System.Collections.Generic;
14 using System.Linq;
15 using System.Text;
16 
17 namespace _11DesignPattern_Observer
18 {
19     /// <summary>
20     /// 具体的订阅者类
21     /// </summary>
22     public class Observer :IObserver
23     {
24         /// <summary>
25         /// 订阅者名字
26         /// </summary>
27         private string m_Name;
28         public string Name
29         {
30             get { return m_Name; }
31             set { m_Name = value; }
32         }
33 
34         /// <summary>
35         /// 订阅者构造函数
36         /// </summary>
37         /// <param name="name">订阅者名字</param>
38         public Observer(string name)
39         {
40             this.m_Name = name;
41         }
42 
43         /// <summary>
44         /// 订阅者接受函数
45         /// </summary>
46         /// <param name="blog"></param>
47         public void Receive(Blog blog)
48         {
49             Console.WriteLine("订阅者:\"{0}\"观察到了:{1}发布的一篇博客,标题为:{2},内容为:{3}",Name,blog.BlogName,blog.BlogTitle,blog.BlogInfo);
50         }
51     }
52 }

测试代码:

 1 using System;
 2 using System.Collections.Generic;
 3 using System.Linq;
 4 using System.Text;
 5 
 6 namespace _11DesignPattern_Observer
 7 {
 8     class Client
 9     {
10         static void Main(string[] args)
11         {
12             Console.WriteLine("--全部订阅者--");
13             //创建一个JiYF的博客
14             Blog jiyfBlog = new JiYFBlog("JiYF笨小孩","丑小鸭","丑小鸭的故事");
15 
16             //创建订阅者
17             Observer obsZhangsan = new Observer("张三");
18             Observer obsLiSi = new Observer("李四");
19             Observer obsWangwu = new Observer("王五"); 
20 
21             //添加对JiYF博客的订阅者
22             jiyfBlog.AddObserver(obsZhangsan);
23             jiyfBlog.AddObserver(obsLiSi);
24             jiyfBlog.AddObserver(obsWangwu);
25 
26             //通知订阅者
27             jiyfBlog.PublishBlog();
28 
29             Console.WriteLine("--移除订阅者张三--");
30             jiyfBlog.RemoveObserver(obsZhangsan);
31             jiyfBlog.PublishBlog();
32             Console.ReadLine();
33         }
34     }
35 }

运行结果:

《C#设计模式--观察者模式(发布-订阅模式)》 

通常在C#代码中,观察者模式一般采用委托来实现如下所示

委托实现观察者模式

抽象博客类:

 1 /*****************************************************
 2  * ProjectName:  _11DesignPattern_ObserverDelegateTest
 3  * Description:
 4  * ClassName:    Blog
 5  * CLRVersion:   4.0.30319.42000
 6  * Author:       JiYF
 7  * NameSpace:    _11DesignPattern_ObserverDelegateTest
 8  * MachineName:  JIYF_PC
 9  * CreateTime:   2017/5/23 20:48:00
10  * UpdatedTime:  2017/5/23 20:48:00
11 *****************************************************/
12 using System;
13 using System.Collections.Generic;
14 using System.Linq;
15 using System.Text;
16 
17 namespace _11DesignPattern_ObserverDelegateTest
18 {
19     /// <summary>
20     /// 委托充当订阅者接口类
21     /// </summary>
22     /// <param name="sender"></param>
23     public delegate void NotifyEventHandler(object sender);
24 
25     /// <summary>
26     /// 订阅博客基类
27     /// </summary>
28     public class Blog
29     {
30         public NotifyEventHandler NotifyEvent;
31         /// <summary>
32         /// 博主名
33         /// </summary>
34         public string BlogName { get; set; }
35 
36         /// <summary>
37         /// 博客标题
38         /// </summary>
39         public string BlogTitle { get; set; }
40 
41         /// <summary>
42         /// 博客信息
43         /// </summary>
44         public string BlogInfo { get; set; }
45 
46         /// <summary>
47         /// 博客构造函数
48         /// </summary>
49         /// <param name="blogTitle">博客标题</param>
50         /// <param name="blogInfo">博客信息</param>
51         public Blog(string name, string blogTitle, string blogInfo)
52         {
53             this.BlogName = name;
54             this.BlogTitle = blogTitle;
55             this.BlogInfo = blogInfo;
56         }
57 
58         /// <summary>
59         /// 绑定订阅事件
60         /// </summary>
61         /// <param name="ob">订阅者</param>
62         public void AddObserver(NotifyEventHandler observer)
63         {
64             NotifyEvent += observer;
65         }
66 
67         /// <summary>
68         /// 取消绑定订阅
69         /// </summary>
70         /// <param name="observer"></param>
71         public void RemoteObserver(NotifyEventHandler observer)
72         {
73             NotifyEvent -= observer;
74         }
75 
76         /// <summary>
77         /// 发布博客通知
78         /// </summary>
79         public void PublishBlog()
80         {
81             if(NotifyEvent != null)
82             {
83                 NotifyEvent(this);
84             }
85         }
86     }
87 }

具体的博客类

 1 /*****************************************************
 2  * ProjectName:  _11DesignPattern_ObserverDelegateTest
 3  * Description:
 4  * ClassName:    JiYFBlog
 5  * CLRVersion:   4.0.30319.42000
 6  * Author:       JiYF
 7  * NameSpace:    _11DesignPattern_ObserverDelegateTest
 8  * MachineName:  JIYF_PC
 9  * CreateTime:   2017/5/23 20:55:58
10  * UpdatedTime:  2017/5/23 20:55:58
11 *****************************************************/
12 using System;
13 using System.Collections.Generic;
14 using System.Linq;
15 using System.Text;
16 
17 namespace _11DesignPattern_ObserverDelegateTest
18 {
19     /// <summary>
20     /// 具体的订阅博客类
21     /// </summary>
22     public class JiYFBlog : Blog
23     {
24         public JiYFBlog(string name, string blogTitile, string blogInfo)
25             : base(name, blogTitile, blogInfo)
26         {
27 
28         }
29     }
30 }

订阅者类

 1 /*****************************************************
 2  * ProjectName:  _11DesignPattern_ObserverDelegateTest
 3  * Description:
 4  * ClassName:    Observer
 5  * CLRVersion:   4.0.30319.42000
 6  * Author:       JiYF
 7  * NameSpace:    _11DesignPattern_ObserverDelegateTest
 8  * MachineName:  JIYF_PC
 9  * CreateTime:   2017/5/23 20:56:50
10  * UpdatedTime:  2017/5/23 20:56:50
11 *****************************************************/
12 using System;
13 using System.Collections.Generic;
14 using System.Linq;
15 using System.Text;
16 
17 namespace _11DesignPattern_ObserverDelegateTest
18 {
19     /// <summary>
20     /// 具体的订阅者类
21     /// </summary>
22     public class Observer
23     {
24         /// <summary>
25         /// 订阅者名字
26         /// </summary>
27         private string m_Name;
28         public string Name
29         {
30             get { return m_Name; }
31             set { m_Name = value; }
32         }
33 
34         /// <summary>
35         /// 订阅者构造函数
36         /// </summary>
37         /// <param name="name">订阅者名字</param>
38         public Observer(string name)
39         {
40             this.m_Name = name;
41         }
42 
43         /// <summary>
44         /// 订阅者接受函数
45         /// </summary>
46         /// <param name="blog"></param>
47         public void Receive(object obj)
48         {
49             Blog blog = obj as Blog;
50             if (blog != null)
51             {
52                 Console.WriteLine("订阅者:\"{0}\"观察到了:{1}发布的一篇博客,标题为:{2},内容为:{3}", Name, blog.BlogName, blog.BlogTitle, blog.BlogInfo);
53             }
54          }
55     }
56 }

测试代码

 1 using System;
 2 using System.Collections.Generic;
 3 using System.Linq;
 4 using System.Text;
 5 
 6 namespace _11DesignPattern_ObserverDelegateTest
 7 {
 8     class Client
 9     {
10         static void Main(string[] args)
11         {
12             Console.WriteLine("--全部订阅者--");
13             //创建一个JiYF的博客
14             Blog jiyfBlog = new Blog("JiYF笨小孩","丑小鸭","丑小鸭的故事");
15             
16             //创建订阅者
17             Observer obsZhangsan    = new Observer("张三");
18             Observer obsLiSi        = new Observer("李四");
19             Observer obsWangwu      = new Observer("王五"); 
20 
21             //添加对JiYF博客的订阅者
22             jiyfBlog.AddObserver(new NotifyEventHandler(obsZhangsan.Receive));
23             jiyfBlog.AddObserver(new NotifyEventHandler(obsLiSi.Receive));
24             jiyfBlog.AddObserver(new NotifyEventHandler(obsWangwu.Receive));
25 
26             ////通知订阅者
27             jiyfBlog.PublishBlog();
28 
29             Console.WriteLine("---移除订阅者张三--");
30             jiyfBlog.RemoteObserver(new NotifyEventHandler(obsZhangsan.Receive));
31             jiyfBlog.PublishBlog();
32             Console.ReadLine();
33         }
34     }
35 }

运行结果:

 《C#设计模式--观察者模式(发布-订阅模式)》

源代码工程文件下载

 

    原文作者:JiYF
    原文地址: https://www.cnblogs.com/JiYF/p/6896458.html
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