观察者模式

观察者模式

class Program
    {
        static void Main(string[] args)
        {
            ConcreteSubject s = new ConcreteSubject();
            s.Attach(new ConcreteObserver(s, "X"));
            s.Attach(new ConcreteObserver(s, "Y"));
            s.Attach(new ConcreteObserver(s, "Z"));
            s.SubjectState = "ABC";
            s.Notify();
            Console.Read();
        }
    }


    abstract class Subject
    {
        private IList<Observer> observers = new List<Observer>();

        //增加观察者
        public void Attach(Observer observer)
        {
            observers.Add(observer);
        }
        //移除观察者
        public void Detach(Observer observer)
        {
            observers.Remove(observer);
        }
        //通知
        public void Notify()
        {
            foreach (Observer o in observers)
            {
                o.Update();
            }
        }
    }

    //具体通知者
    class ConcreteSubject : Subject
    {
        private string subjectState;

        //具体通知者状态
        public string SubjectState
        {
            get { return subjectState; }
            set { subjectState = value; }
        }
    }


    abstract class Observer
    {
        public abstract void Update();
    }

    class ConcreteObserver : Observer
    {
        private string name;
        private string observerState;
        private ConcreteSubject subject;

        public ConcreteObserver(
          ConcreteSubject subject, string name)
        {
            this.subject = subject;
            this.name = name;
        }
        //更新
        public override void Update()
        {
            observerState = subject.SubjectState;
            Console.WriteLine("观察者{0}的新状态是{1}",
              name, observerState);
        }

        public ConcreteSubject Subject
        {
            get { return subject; }
            set { subject = value; }
        }
    }

烧水事件

   // 热水器
    public class Heater
    {
        private int temperature;
        public string type = "RealFire 001";              // 添加型号作为演示
        public string area = "China Xian";                     // 添加产地作为演示
        //声明委托
        public delegate void BoiledEventHandler(Object sender, BoliedEventArgs e);
        public event BoiledEventHandler Boiled;       //声明事件

        // 定义BoliedEventArgs类，传递给Observer所感兴趣的信息
        public class BoliedEventArgs : EventArgs
        {
            public readonly int temperature;
            public BoliedEventArgs(int temperature)
            {
                this.temperature = temperature;
            }
        }

        // 可以供继承自 Heater 的类重写，以便继承类拒绝其他对象对它的监视
        protected virtual void OnBolied(BoliedEventArgs e)
        {
            if (Boiled != null)
            {       // 如果有对象注册
                Boiled(this, e);       // 调用所有注册对象的方法
            }
        }

        // 烧水。
        public void BoilWater()
        {
            for (int i = 0; i <= 100; i++)
            {
                temperature = i;
                if (temperature > 95)
                {
                    //建立BoliedEventArgs 对象。
                    BoliedEventArgs e = new BoliedEventArgs(temperature);
                    OnBolied(e);       // 调用 OnBolied方法
                }
            }
        }
    }

    // 警报器
    public class Alarm
    {
        public void MakeAlert(Object sender, Heater.BoliedEventArgs e)
        {
            Heater heater = (Heater)sender;              //这里是不是很熟悉呢？
            //访问 sender 中的公共字段
            Console.WriteLine("Alarm：{0} - {1}: ", heater.area, heater.type);
            Console.WriteLine("Alarm: 嘀嘀嘀，水已经 {0} 度了：", e.temperature);
            Console.WriteLine();
        }

    }

    // 显示器
    public class Display
    {
        public static void ShowMsg(Object sender, Heater.BoliedEventArgs e)
        {       //静态方法
            Heater heater = (Heater)sender;
            Console.WriteLine("Display：{0} - {1}: ", heater.area, heater.type);
            Console.WriteLine("Display：水快烧开了，当前温度：{0}度。", e.temperature);
            Console.WriteLine();
        }
    }

    class Program
    {
        static void Main()
        {
            Heater heater = new Heater();
            Alarm alarm = new Alarm();

            heater.Boiled += alarm.MakeAlert;       //注册方法
            heater.Boiled += (new Alarm()).MakeAlert;              //给匿名对象注册方法
            heater.Boiled += new Heater.BoiledEventHandler(alarm.MakeAlert);       //也可以这么注册
            heater.Boiled += Display.ShowMsg;              //注册静态方法

            heater.BoilWater();       //烧水，会自动调用注册过对象的方法
            Console.Read();
        }
    }

猫叫事件

http://www.tracefact.net/Design-Pattern/Observer.aspx

http://www.cnblogs.com/sjrhero/archive/2011/01/07/1930230.html