Observer Pattern浅谈

1.观察者模式:

定义对象间的一种一对多的依赖关系。当一个对象的状态发生改变时，所有依赖于它的对象都能得到通知并被自动更新。

2.设计原则：

为了交互对象之间的松耦合设计而努力。

3.Observer接口:

    public interface Observer
    {
        void Update(string content);
    }

4.ConcreteObserver类:

    public class Reader : Observer
    {

        private string _reader;
        public string ReaderName
        {
            get { return _reader; }
            set { _reader = value; }
        }

        public Reader(Subject sb, string reader)
        {
            sb.AddObserver(this);
            _reader = reader;
        }

        #region Observer Members

        public void Update(string content)
        {
            Console.WriteLine(_reader + ",收到新的订阅:" + content);
        }

        #endregion
    }

5.Subject接口:

    public interface Subject
    {
        /// <summary>
        /// 添加观察者
        /// </summary>
        /// <param name="ob"></param>
        void AddObserver(Observer ob);

        /// <summary>
        /// 移除观察者
        /// </summary>
        /// <param name="ob"></param>
        void RemoveObserver(Observer ob);

        /// <summary>
        /// 通知所有观察者
        /// </summary>
        /// <param name="contenr"></param>
        void NotifyObserver(string content);
    }

6.ConcreteSubject类:

    public class NewsPaper : Subject
    {
        List<Observer> list = new List<Observer>();

        #region Subject Members

        public void AddObserver(Observer ob)
        {
            list.Add(ob);
        }

        public void RemoveObserver(Observer ob)
        {
            list.Remove(ob);
        }

        public void NotifyObserver(string content)
        {
            foreach (Observer ob in list)
            {
                ob.Update(content);
            }
        }

        #endregion

        public void Publish(string content)
        {
            NotifyObserver(content);
        }
    }

7.测试：

        static void Main(string[] args)
        {
            NewsPaper np = new NewsPaper();
            Reader rd1 = new Reader(np, "小王");
            Reader rd2 = new Reader(np, "小张");
            np.Publish("这是最新发布的消息");

            Console.ReadLine();
        }