《大话设计模式》学习笔记10：观察者模式

　　

　　

观察老板回来示例：

　　

1.Subject：

    public interface Subject
    {
        void Attach(Observer observer);
        void Detach(Observer observer);
        void Notify();
        string SubjectState { get; set; }
    }

2.ConcreteSubject（以Boss为例）:

    public class Boss:Subject
    {
        private IList<Observer> observers = new List<Observer>();
        public void Attach(Observer observer)
        {
            observers.Add(observer);
        }

        public void Detach(Observer observer)
        {
            observers.Remove(observer);
        }

        public void Notify()
        {
            foreach(var o in observers)
            {
                o.Update();
            }
        }

        public string SubjectState { get; set; }
    }

3.ObServer：

    public abstract class Observer
    {
        protected string name;
        protected Subject subject;
        public Observer(string name,Subject subject)
        {
            this.name = name;
            this.subject = subject;
        }
        public abstract void Update();
    }

4.ConcreteObserver：

    public class StockObserver:Observer
    {
        public StockObserver(string name,Subject subject):base(name,subject)
        {

        }
        public override void Update()
        {
            Console.WriteLine("{0},{1},关闭股票行情，继续工作！", subject.SubjectState, name);
        }
    }

    public class NBAObserver:Observer
    {
        public NBAObserver(string name,Subject subject):base(name,subject)
        {

        }
        public override void Update()
        {
            Console.WriteLine("{0},{1},关闭NBA直播，继续工作！", subject.SubjectState, name);
        }
    }

5.客户端代码：

    class Program
    {
        static void Main(string[] args)
        {
            Boss boss = new Boss();
            StockObserver stockObserver = new StockObserver("张三",boss);
            NBAObserver nbaObserver = new NBAObserver("李四",boss);
            boss.Attach(stockObserver);
            boss.Attach(nbaObserver);
            //boss.Detach(nbaObserver);

            boss.SubjectState = "老板回来啦";
            boss.Notify();
        }
    }

使用委托实现观察者模式：

1.Subject：

    public interface Subject
    {
        void Notify();
        string SubjectState{get;set;}
    }

2.声明委托：

public delegate void UpdateEventHandler();

3.ConcreteSubject（以Boss为例）:

    public class Boss:Subject
    {
        public UpdateEventHandler Update;
        public void Notify()
        {
            Update();
        }
        public string SubjectState { get; set; }
    }

4.ConcreteObserver：

    public class StockObserver
    {
        private string name;
        private Subject subject;
        public StockObserver(string name,Subject subject)
        {
            this.name = name;
            this.subject = subject;
        }
        public void CloseStockMarket()
        {
            Console.WriteLine("{0},{1},关闭股票行情，继续工作！", subject.SubjectState, name);
        }
    }

    public class NBAObserver
    {
        private string name;
        private Subject subject;
        public NBAObserver(string name, Subject subject)
        {
            this.name = name;
            this.subject = subject;
        }
        public void CloseNBADirectSeeding()
        {
            Console.WriteLine("{0},{1},关闭NBA直播，继续工作！", subject.SubjectState, name);
        }
    }

5.客户端代码：

    class Program
    {
        static void Main(string[] args)
        {
            Boss boss = new Boss();
            StockObserver stockObserver = new StockObserver("张三", boss);
            NBAObserver nbaObserver = new NBAObserver("李四", boss);
            //boss.Update = new UpdateEventHandler(stockObserver.CloseStockMarket);
            //boss.Update += new UpdateEventHandler(nbaObserver.CloseNBADirectSeeding);
            boss.Update = stockObserver.CloseStockMarket;
            boss.Update += nbaObserver.CloseNBADirectSeeding;

            boss.SubjectState = "老板回来啦";
            boss.Notify();
        }
    }