using System;
using System.Collections.Generic;

namespace Demo
{
    #region 抽象層,定義了觀察者模式
    /// <summary>
    /// （抽象）新聞
    /// </summary>
    public interface INews
    {
        void SubScribe(ISubscriber s);
        void UnSubScribe(ISubscriber s);
        void Publish(string newsTitle);   //在具體實現的過程中建立發布與訂閱的聯系
    }

    /// <summary>
    /// (抽象）訂閱者
    /// </summary>
    public interface ISubscriber
    {
        void Read(string newsTitle);
    }
    #endregion

    #region 實現層,是對抽象層的具體實現
    /// <summary>
    /// （具體）新聞
    /// </summary>
    public class ITNews : INews
    {
        private List<ISubscriber> readers = new List<ISubscriber>();

        public void SubScribe(ISubscriber s)
        {
            readers.Add(s);
        }

        public void UnSubScribe(ISubscriber s)
        {
            if (readers.Count >= 0)
            {
                readers.Remove(s);
            }
        }

        public void Publish(string newsTitle)
        {
            foreach (ISubscriber i in readers)
            {
                i.Read(newsTitle);          //<<<<<發布的時候訂閱>>>>>
            }
        }
    }

    /// <summary>
    /// (具體)訂閱者
    /// </summary>
    public class Subscriber : ISubscriber
    {
        private string subscriber = string.Empty;
        public Subscriber(string subscriber)
        {
            this.subscriber = subscriber;
        }

        public void Read(string newsTitle)
        {
            Console.WriteLine(string.Format("{0}閱讀了IT新聞/"{1}/"", subscriber, newsTitle));
        }
    }
    #endregion

    public class Pro
    {
        static void Main(string[] args)
        {
            ITNews news = new ITNews();
            Subscriber zs = new Subscriber("張三"),
                                 ls = new Subscriber("李四"),
                                 ww = new Subscriber("王五");

            news.SubScribe(zs);
            news.SubScribe(ls);
            news.SubScribe(ww);
            news.UnSubScribe(ls);  //張三取消訂閱

            news.Publish("2014年移動電商攻堅戰：阿里巴巴如何破局？");
            news.Publish("余額寶還能重回高收益率嗎？");

            Console.WriteLine();
            Console.ReadKey();
        }
    }
}