观察者模式（C#实现）

http://www.cnblogs.com/wyixin/archive/2011/12/11/2284313.html

首先实现两个接口：Subject（用于发布信息） Observer（信息接受者）

Subject中：

registerObserver(Observer observer);   用于登记需要推送的用户

removeObserver(Observer observer);   将用户剔除出推送列表

notifyObserver();                   推送服务

Observer中：

update(string  news);          当Subject信息发送时，用于更新

然后用 Newsstand类和Commenpeolpe类分别实现Subject,Observer

 

____________________________________________________________________________________实现如下

public interface Subject
    {
         void registerObserver(Observer observer);
         void removeObserver(Observer observer);
         void notifyObserver();
    }

----------------------------------------------------------------------

public interface Observer
    {
       void update(string  news);
    }

----------------------------------------------------------------------------

public class Newsstand:Subject
    {
        private string newsOfToday; //用于推送的消息
        private ArrayList observerList = null;//定义数组，储存观察者对象
        public Newsstand()
        {
            observerList = new ArrayList();
        }
        public void registerObserver(Observer observer)
        {
            observerList.Add(observer);
        }
 
        public void removeObserver(Observer observer)
        {
            if (this.observerList.IndexOf(observer) != 0)
                observerList.Remove(observer);
        }
 
        public void notifyObserver()//当消息更新时自动发送给观察者
        {
            for (int i = 0; i < observerList.ToArray().Length; i++)
            {
                Observer observer =(Observer) observerList[i];
                observer.update(this.newsOfToday);
            }
        }
        public void newsChanged()
        {
            notifyObserver();
        }
        public void setNews(string news)//得到消息，处理更新
        {
            this.newsOfToday = news;
            newsChanged();
        }
    }

-----------------------------------------------------------------------------------------------------------

 public class Commonpeople:Observer
    {
        private Subject newsstand;
        private string newsFromNewsStand;
        public Commonpeople() { }
        public Commonpeople(Subject newsstand)//使用上下文中的信息发布者初始化时
        {
            this.newsstand = newsstand;
            this.newsstand.registerObserver(this);
        }
        public void update(string news)//自动取得更新数据
        {
            this.newsFromNewsStand = news;
            display();
        }
        private void display()
        {
            Console.WriteLine(this.newsFromNewsStand);
        }
    }

------------------------------------------------------------------------------

static void Main(string[] args)//主程序
        {
            Newsstand newsStand = new Newsstand();
            Commonpeople peopleWhoGetTheNews = new Commonpeople(newsStand);
            Commonpeople peopleWhoDonotFeed = new Commonpeople(newsStand);
            Commonpeople people = new Commonpeople();
            newsStand.setNews("2011-11-11");
            newsStand.removeObserver(peopleWhoDonotFeed);
            newsStand.setNews("2012-12-24");
        }