(C#)设计模式 之 观察者模式 (经典应用:猫叫,烧开水)

/*
* 题目：
* 猫叫了，所有老鼠开始逃跑，主人被惊醒，请用OO的思想描绘此过程
* 1，老鼠跟主人是被动的
* 2，要考虑联动性与扩展性
*/
using System;
using System.Collections.Generic;
using System.Text;
namespace CatCry
{
/*委托，当猫叫时将信息传给所有观察者*/
public delegate void CatCryEventHandler(object sender, EventArgs e);
/*被观察对象*/
abstract class Subject
{
public event CatCryEventHandler CatCryEvent;//猫叫时的事件
public void Cry(EventArgs e)
{
this.CatCryEvent(this, e);
}
public void Cry()
{
//不接收猫叫时发出的信息
this.CatCryEvent(this, new EventArgs());
}
}
/*观察者*/
abstract class Observer
{
public Observer() { }
public Observer(Subject subject)
{
subject.CatCryEvent += new CatCryEventHandler(this.Notified);
}
//当猫叫时做出的反应（当收到通知时）
abstract protected void Notified(object sender, EventArgs e);
}
/*定义猫作为被观察对象*/
class Cat : Subject
{
public Cat() { Console.WriteLine("猫叫了"); }
}
/*定义老鼠作为观察者*/
class Mouse : Observer
{
string mouseName;
public Mouse() { }
public Mouse(string mouseName, Subject subject)
: base(subject)
{
this.mouseName = mouseName;
}
override protected void Notified(object sender, EventArgs e)
{
Console.WriteLine(this.mouseName + "开始逃跑");
}
}
/*定义主人作为观察者*/
class Marster : Observer
{
public Marster() { }
public Marster(Subject subject) : base(subject) { }
override protected void Notified(object sender, EventArgs e)
{
Console.WriteLine("主人被惊醒了");
}
}
/// <summary>
/// 功能：用观察者模式实现
/// 作者：allnen
/// 时间：2008-6-5
/// </summary>
class Program
{
static void Main(string[] args)
{
Cat cat = new Cat();
Mouse m1 = new Mouse("老鼠1", cat);
Mouse m2 = new Mouse("老鼠2", cat);
Marster marster = new Marster(cat);
cat.Cry();//猫叫了
}
}
}

/*
* code 烧开水
*/
using System;
using System.Collections.Generic;
using System.Text;
namespace Delegate
{
// 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, BoiledEventArgs e);
public event BoiledEventHandler Boiled; //声明事件
// 定义BoiledEventArgs类，传递给Observer所感兴趣的信息
public class BoiledEventArgs : EventArgs
{
public readonly int temperature;
public BoiledEventArgs(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 OnBoiled(BoiledEventArgs 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BoiledEventArgs 对象。
BoiledEventArgs e = new BoiledEventArgs(temperature);
OnBoiled(e); // 调用 OnBolied方法
}
}
}
}
// 警报器
public class Alarm
{
public void MakeAlert(Object sender, Heater.BoiledEventArgs 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.BoiledEventArgs 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
}
}
}
//输出为：
//Alarm：China Xian - RealFire 001:
//Alarm: 嘀嘀嘀，水已经 96 度了：
//Alarm：China Xian - RealFire 001:
//Alarm: 嘀嘀嘀，水已经 96 度了：
//Alarm：China Xian - RealFire 001:
//Alarm: 嘀嘀嘀，水已经 96 度了：
//Display：China Xian - RealFire 001:
//Display：水快烧开了，当前温度：96度。