Decorator Pattern (3)
装饰模式（3）
设计模式原则：
对于类，我们要做到易于扩展、修改闭合。
装饰模式：
为对象动态添加属性，提供一种可以替代继承来扩展类功能的方法。
示例代码：
using System;
using
System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using
System.Security.Cryptography;
namespace Hello
{
//饮料抽象类
public
abstract class Beverage
{
protected
string description = "Unknow
beverage";
public
virtual string
GetDescription()
{
return
description;
}
public
abstract double
Cost();
}
//香料装饰
public
abstract class CondimentDecorator : Beverage
{
public
abstract override
string GetDescription();
}
//Espresso
public
class Espresso
: Beverage
{
public
Espresso()
{
description = "Espresso";
}
public
override double
Cost()
{
return
1.99;
}
}
//HouseBlend
public
class HouseBlend
: Beverage
{
public
HouseBlend()
{
description = "HouseBlend";
}
public
override double
Cost()
{
return
0.89;
}
}
//Condiment
Mocha
public
class Mocha
: CondimentDecorator
{
Beverage
beverage;
public
Mocha(Beverage beverage)
{
this.beverage
= beverage;
}
public
override string
GetDescription()
{
return
beverage.GetDescription() + ",Mocha";
}
public
override double
Cost()
{
return
beverage.Cost() + 0.2;
}
}
//Condiment
Milk
public
class Milk :
CondimentDecorator
{
Beverage
beverage;
public
Milk(Beverage beverage)
{
this.beverage
= beverage;
}
public
override string
GetDescription()
{
return
beverage.GetDescription() + ",Milk";
}
public
override double
Cost()
{
return
beverage.Cost() + 0.6;
}
}
//
class
Program
{
static
void Main(string[]
args)
{
Beverage
myBeverage = new HouseBlend();
myBeverage = new Mocha(myBeverage);
Console.WriteLine(myBeverage.GetDescription());
Console.WriteLine(myBeverage.Cost());
Beverage
myBeverage2 = new Espresso();
myBeverage2 = new Milk(myBeverage2);
myBeverage2 = new Mocha(myBeverage2);
Console.WriteLine(myBeverage2.GetDescription());
Console.WriteLine(myBeverage2.Cost());
}
}
}
