观察者模式 实例

         观察者模式在软件重构中会常常被使用，下面写出一个实例便于理解.. 

using System;
 using System.Collections;

 namespace moniter
{
    public interface objserver
    { 
        void Action();
    }
    public interface subject
    {
        void At(objserver obj);
    }

    public class objserverA:objserver
    { 
        public objserverA(subject s)
        {
            s.At(this);        
        }
        public void Action()
        {
            Console.WriteLine("我是观察者A！");
        }
    }
    public class objserverB:objserver
    {
        public objserverB(subject s)
        {
            s.At(this);
        }
        public void Action()
        {
            Console.WriteLine("我是观察者B！");
        }
    }
    public class objSubject : subject
    {
        ArrayList objs;
        public objSubject()
        {
            this.objs = new ArrayList();
        }

        public void At(objserver obj)
        {
            objs.Add(obj);
        }
        public void SubjectAction()
        {
            Console.WriteLine("我是被监视者，观察者报名！");
            foreach (objserver o in objs)
            {
                o.Action();
            }
        }

    }
    class Program
    {
        static void Main(string[] args)
        {
            objSubject os = new objSubject();
            objserverA oa = new objserverA(os);
            objserverB ob = new objserverB(os);
            os.SubjectAction();
            Console.ReadLine();
        }
    }
}
 

执行结果： 

我是被监视者，观察者报名！

我是观察者A！

我是观察者B！