class1.cs

《深入浅出设计模式》的完整源代码

using System;
using System.Collections;
//被观察对象--个股
abstract class Stock
{
	protected string symbol;
	protected double price;
	private ArrayList investors = new ArrayList();
	public Stock( string symbol, double price )
	{
		this.symbol = symbol;
		this.price = price;
	}
	//附加要通知的投资者
	public void Attach( Investor investor )
	{
		investors.Add( investor );
	}
	//分离要通知的投资者
	public void Detach( Investor investor )
	{
		investors.Remove( investor );
	}
	//通知所需要知会的投资者
	public void Notify()
	{
		foreach( Investor i in investors )
			i.Update( this );
	}
	//股价
	public double Price
	{
		get{ return price; }
		set
		{
			price = value;
			Notify(); }
	}
	//个股标志
	public string Symbol
	{
		get{ return symbol; }
		set{ symbol = value; }
	}
}

//具体被观察对象
class IBM : Stock
{
	// Constructor
	public IBM( string symbol, double price )
		: base( symbol, price ) {}
}
//观察者
interface IInvestor
{
	// Methods
	void Update( Stock stock );
}
//具体观察者
class Investor : IInvestor
{
	private string name;
	private string observerState;
	private Stock stock;
	public Investor( string name )
	{
		this.name = name;
	}
	public void Update( Stock stock )
	{
		Console.WriteLine( "通知到股民 {0} {1}最新股价为： {2:C}", name, stock.Symbol, stock.Price );
	}

	// Properties
	public Stock Stock
	{
		get{ return stock; }
		set{ stock = value; }
	}
}

/// <summary>
/// ObserverApp test
/// </summary>
public class ObserverApp
{
	public static void Main( string[] args )
	{
		//创建股民
		Investor s = new Investor( "张三" );
		Investor b = new Investor( "李四" );
		//创建个股IBM并且附加上投资的股民
		IBM ibm = new IBM( "IBM", 120.00 );
		ibm.Attach( s );
		ibm.Attach( b );
		//变更股价，其投资的所有股民都得到知会
		ibm.Price = 120.10;
		ibm.Price = 121.00;
		ibm.Price = 120.50;
		ibm.Price = 120.75;
		Console.Read();
	}
}