Observer观察者设计模式

Observer设计模式主要包括以下两种对象:

(1)被观察对象:Subject,它往往包含其他对象感兴趣的东西,上面例子中热水器中就是Subject(被监视对象);

(2)观察对象:Observer,它观察着Subject,当Subject中的某件事发生后,会告知Observer,Obersver会采取相应的行动。上面例子中显示器和报警器就是观察对象,当油箱中温度大于95°时,报警器和显示器就会做出相应的警报;

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ObserverApp
{
    class Program
    {
        static void Main(string[] args)
        {
            Oil o = new Oil();
            o.BoiledEvent += new Alarm().MakeAlarm;//先往Oil对象中注册事件
            o.BoiledEvent += new Display().ShowMsg;//先往Oil对象中注册事件
            o.BoilWater();//执行主要方法,等到条件合适在触发上面注册的事件
        }
    }

    /// <summary>
    /// Subject被观察对象   ---Oil热水器
    /// </summary>
    internal class Oil
    {
        /// <summary>
        /// 牌子
        /// </summary>
        public string brand = "Nick";

        /// <summary>
        /// 价格
        /// </summary>
        public int price = 1000;

        public delegate void BoiledHandler(object obj, EventArgs args);
        public event BoiledHandler BoiledEvent;

        /// <summary>
        /// 将观察者感兴趣的信息通过实例传递过去
        /// </summary>
        public class BoilEventArgs : EventArgs 
        {
            public int Temperature { get; set; }
            public BoilEventArgs(int temperature) 
            {
                this.Temperature = temperature;
            }
        }

        public void BoilWater() 
        {
            for (int i = 0; i <= 100; i++) 
            {
                if (i >= 95) 
                {
                    BoilEventArgs args = new BoilEventArgs(i);
                    BoiledEvent(this, args);//当温度达到95度及以上的时候,触发所有订阅该事件的观察者的方法
                }
            }
        }
    }

    /// <summary>
    /// Observer观察对象   ---警报器
    /// </summary>
    internal class Alarm 
    {
        public void MakeAlarm(object sender,EventArgs args) 
        {
            Oil o = (Oil)sender;
            ObserverApp.Oil.BoilEventArgs a = (ObserverApp.Oil.BoilEventArgs)args;
            Console.WriteLine("Alarm:嘀嘀嘀,水已经 {0} 度了,当前热水器的牌子是{1},价格是{2}",a.Temperature, o.brand, o.price);
        }
    }

    /// <summary>
    /// Observer观察对象   ---显示器
    /// </summary>
    internal class Display
    {
        public void ShowMsg(object sender, EventArgs args)
        {
            Oil o = (Oil)sender;
            ObserverApp.Oil.BoilEventArgs a = (ObserverApp.Oil.BoilEventArgs)args;
            Console.WriteLine("Display:水已烧开,当前温度:{0}度,当前热水器的牌子是{1},价格是{2}", a.Temperature, o.brand, o.price);
            Console.ReadKey();
        }
    }
}