行为型---中介者模式（Mediator Pattern）

中介者模式的定义

中介者模式，定义了一个中介对象来封装一系列对象之间的交互关系。中介者使各个对象之间不需要显式地相互引用，从而使耦合性降低，而且可以独立地改变它们之间的交互行为。  

中介者模式的结构

　　从生活中例子自然知道，中介者模式设计两个具体对象，一个是用户类，另一个是中介者类，根据针对接口编程原则，则需要把这两类角色进行抽象，所以中介者模式中就有了4类角色，它们分别是：抽象中介者角色，具体中介者角色、抽象同事类和具体同事类。中介者类是起到协调各个对象的作用，则抽象中介者角色中则需要保存各个对象的引用。有了上面的分析，则就不难理解中介者模式的结构图了，具体结构图如下所示：

namespace ConsoleApplication1
{
/// <summary>
/// 抽象中介者
/// </summary>
public abstract class AbstractMediator
{
protected Purchase purchase;
protected Sale sale;
protected Stock stock;

public AbstractMediator()
{
purchase = new Purchase(this);
sale = new Sale(this);
stock = new Stock(this);
}
//中介者最重要的方法叫做事件方法,处理多个对象之间的关系
public abstract void execute(string strFun, params object[] arg);
}

/// <summary>
/// 具体中介者
/// </summary>
public class Mediator : AbstractMediator
{
public override void execute(string strFun, params object[] arg)
{
switch (strFun)
{
case "purchase.buy": //采购电脑
this.buyComputer(Convert.ToInt32(arg[0]));
break;
case "sale.sell": //销售电脑
this.sellComputer(Convert.ToInt32(arg[0]));
break;
case "sale.offsell": //折价销售
this.offSell();
break;
case "stock.clear": //清仓处理
this.clearStock();
break;
default:
break;
}
}

//采购电脑
private void buyComputer(int number)
{
int saleStatus = sale.getSaleStatus();
if (saleStatus > 80) //销售情况良好
{
Console.WriteLine("采购IBM电脑" + number + "台");
stock.increase(number);
}
else  //销售情况不好
{
int buynumber = number / 2;
Console.WriteLine("采购IBM电脑" + number + "台");
}
}
//销售电脑
private void sellComputer(int number)
{
if (stock.getStockNumber() < number)  //库存数量不够销售
{
purchase.buyIBMcomputer(number);
}
stock.decrease(number);
}
//折价销售电脑
private void offSell()
{
Console.WriteLine("折价销售IBM电脑" + stock.getStockNumber() + "台");
}
//清仓处理
private void clearStock()
{
//要求清仓销售
sale.offSale();
//要求采购人员不要采购
purchase.refuseBuyIBM();
}
}

/// <summary>
/// 抽象同事类
/// </summary>
public abstract class AbstractColleague
{
protected AbstractMediator mediator;
public AbstractColleague(AbstractMediator _mediator)
{
this.mediator = _mediator;
}
}

/// <summary>
/// 具体同事类--采购类
/// </summary>
public class Purchase : AbstractColleague
{
public Purchase(AbstractMediator _mediator)
: base(_mediator)
{

}
//采购IBM电脑
public void buyIBMcomputer(int number)
{
mediator.execute("purchase.buy", number);
}
//不再采购IBM电脑
public void refuseBuyIBM()
{
Console.WriteLine("不再采购IBM电脑");
}
}

/// <summary>
/// 具体同事类--库存管理类
/// </summary>
public class Stock : AbstractColleague
{
//模拟期初库存数
private static int COMPUTER_NUMBER = 100;
public Stock(AbstractMediator _mediator)
: base(_mediator)
{

}
//库存增加
public void increase(int number)
{
COMPUTER_NUMBER = COMPUTER_NUMBER + number;
Console.WriteLine("库存数量为:" + COMPUTER_NUMBER);
}
//库存减少
public void decrease(int number)
{
COMPUTER_NUMBER = COMPUTER_NUMBER - number;
Console.WriteLine("库存数量为:" + COMPUTER_NUMBER);
}
//获取库存数量
public int getStockNumber()
{
return COMPUTER_NUMBER;
}

/*
* 存货压力大了，
* 就需要通知采购人员不要采购，
* 销售人员要尽快销售
*/
public void clearStock()
{
Console.WriteLine("清理存货是数量为:" + COMPUTER_NUMBER);
mediator.execute("stock.clear");
}
}

/// <summary>
/// 具体同事类--销售管理类
/// </summary>
public class Sale : AbstractColleague
{
public Sale(AbstractMediator _mediator)
: base(_mediator)
{

}
//销售IBM电脑
public void SellIBMComputer(int number)
{
mediator.execute("sale.sell",number);
Console.WriteLine("销售IBM电脑" + number);
}
//反馈销售情况,0~100变化,0代表根本就没人买,100代表非常畅销
public int getSaleStatus()
{
Random rand = new Random();
int saleStatus = rand.Next(100);
Console.WriteLine("IBM电脑的销售情况为:" + saleStatus);
return saleStatus;
}
//折价处理
public void offSale()
{
mediator.execute("sale.offsell");
}

}

class Program
{
static void Main(string[] args)
{
AbstractMediator mediator = new Mediator();
//采购人员采购电脑
Console.WriteLine("---------采购人员采购电脑---------");
Purchase purchase = new Purchase(mediator);
purchase.buyIBMcomputer(100);
//销售人员销售电脑
Console.WriteLine("---------销售人员销售电脑---------");
Sale sale = new Sale(mediator);
sale.SellIBMComputer(1);
//库存管理人员管理库存
Console.WriteLine("---------库存管理人员管理库存---------");
Stock stock = new Stock(mediator);
stock.clearStock();
Console.ReadLine();
}
}
}

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