装饰者模式（C#）实现
我喜欢户外，然后常常去逛户外装备的店子，一般买了自行车等大件，再买登山包，登山鞋等配件就会有优惠。比如买了辆Giant的车，然后买个bag就有优惠，本案例将配件作为装饰者，简单的实现装饰者模式，对于继承，多态掌握的还是很迷惑。有错误还请各位看官帮忙指出，仪器共同进步！
首先定义一个超类Buybike
public abstract class Buybike
{
protected string description="To Get a Bike";
public virtual string getDescription()
{
return description;
}
public abstract string Cost();
}
超类下面定义一个装饰者超类OtherDecorator（所有装饰者【案例中配件】的父类）
public abstract class OtherDecorator:Buybike
{
//只是为了将装饰者全部置于其下，无具体实现方法
}
下面是两个被装饰的类Giant Merida（捷安特，美利达）
class Merida:Buybike
{
public Merida()
{
description = "Merida";
}
public override string Cost()
{
return "2000RMB";
}
}
public class Giant : Buybike
{
public Giant()
{
description = "Giant";
}
public override string Cost()
{
return "3000RMB";
}
}
接下去是所有装饰者（配件），全部继承自OtherDecorator
class AddShirt:OtherDecorator
{
private Buybike buyBike;
public AddShirt(Buybike buyBike)
{
this.buyBike = buyBike;
}
public override string getDescription()
{
return buyBike.getDescription() + "Add a shirt";
}
public override string Cost()
{
return buyBike.Cost() + "shirt's money:600RMB";
}
}
class AddShoes:OtherDecorator
{
private Buybike buyBike;
public AddShoes(Buybike buyBike)
{
this.buyBike = buyBike;
}
public override string getDescription()
{
return buyBike.getDescription() + "Add a shoes";
}
public override string Cost()
{
return buyBike.Cost() + "shoe's money:300RMB";
}
}
class AddBag:OtherDecorator
{
private Buybike buyBike;
public AddBag(Buybike buyBike)
{
this.buyBike = buyBike;
}
public override string getDescription()
{
return buyBike.getDescription() + "Add a bag";
}
public override string Cost()
{
return buyBike.Cost() + "bag's money:200RMB";
}
}
程序运行如下：
class Program
{
static void Main(string[] args)
{
Buybike a= new Giant();
a = new AddBag(a);
a = new AddShirt(a);
Console.WriteLine(a.Cost());
Console.WriteLine(a.getDescription());
}
}
此模式好处：装饰者和被装饰者从相同基类派生，类型之间的转化非常方便，适合多态的实现。
具体到例子，此处的a具体到是一个基类变量，把它指到下面的子类不必进行类型转化，而且a具体是什么类型，得在运行时才能确定，程序耦合度大大降低。