设计模式（十）————装饰者模式（Decorator Pattern）

最新推荐文章于 2025-04-24 15:45:42 发布

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本文深入解析装饰者模式，一种在不改变对象结构的前提下，动态扩展其功能的设计模式。通过C++和C#代码实例，展示了如何使用装饰者模式为咖啡饮料添加不同的配料，从而增加其功能和价格。

定义：动态地给一个对象添加一些额外的职责。就增加功能来说，装饰者模式相比生成子类更加灵活。
UML类图：

C++实现：

#include<iostream>
#include<string>
using namespace std;

class Beverage
{
public:
	string description = "Unkonw Beverage";
	virtual string getDescription()
	{
		return description;
	}
	virtual double cost() = 0;
	virtual ~Beverage() {}
};
class ComdimentDecorator :public Beverage
{
public :
	virtual ~ComdimentDecorator() {}
};
class Espresso : public Beverage
{
public:
	Espresso()
	{
		description = "Espressp Coffee";
	}
	double cost() override
	{
		return 1.99;
	}
	virtual ~Espresso() {}
};
class HouseBlend : public Beverage
{
public:
	HouseBlend()
	{
		description = "House Blend Coffee";
	}
	double cost() override
	{
		return 0.89;
	}
	virtual ~HouseBlend() {}
};
class DarkRoast : public Beverage
{
public:
	DarkRoast()
	{
		description = "Dark Roast Coffee";
	}
	double cost() override
	{
		return 0.99;
	}
	virtual ~DarkRoast() {}
};
class Decaf : public Beverage
{
public:
	Decaf()
	{
		description = "Decaf Coffee";
	}
	double cost() override
	{
		return 1.05;
	}
	virtual ~Decaf() {}
};
class Mocha : public ComdimentDecorator
{
	Beverage* beverage;
public:
	Mocha(Beverage* beverage)
	{
		this->beverage = beverage;
	}
	double cost() override
	{
		return this->beverage->cost() + 0.2;
	}
	string getDescription() override
	{
		return this->beverage->getDescription() + ", Mocha";
	}
	virtual ~Mocha() {}
};
class Milk : public ComdimentDecorator
{
	Beverage* beverage;
public:
	Milk(Beverage* beverage)
	{
		this->beverage = beverage;
	}
	double cost() override
	{
		return this->beverage->cost() + 0.1;
	}
	string getDescription() override
	{
		return this->beverage->getDescription() + ", Milk";
	}
	virtual ~Milk() {}
};
class Soy : public ComdimentDecorator
{
	Beverage* beverage;
public:
	Soy(Beverage* beverage)
	{
		this->beverage = beverage;
	}
	double cost() override
	{
		return this->beverage->cost() + 0.15;
	}
	string getDescription() override
	{
		return this->beverage->getDescription() + ", Soy";
	}
	virtual ~Soy() {}
};
class Whip :public ComdimentDecorator
{
	Beverage* beverage;
public:
	Whip(Beverage* beverage)
	{
		this->beverage = beverage;
	}
	double cost() override
	{
		return this->beverage->cost() + 0.1;
	}
	string getDescription() override
	{
		return this->beverage->getDescription() + ", Whip";
	}
	virtual ~Whip() {}
};

int main()
{
	Beverage* beverage = new Espresso();
	cout << beverage->getDescription() << "\n" << beverage->cost() << endl;

	Beverage* beverage2 = new DarkRoast();
	beverage2 = new Mocha(beverage2);
	beverage2 = new Mocha(beverage2);
	beverage2 = new Whip(beverage2);
	cout << beverage2->getDescription() << "\n" << beverage2->cost() << endl;

	Beverage* beverage3 = new HouseBlend();
	beverage3 = new Soy(beverage3);
	beverage3 = new Mocha(beverage3);
	beverage3 = new Whip(beverage3);
	cout << beverage3->getDescription() << "\n" << beverage3->cost() << endl;
	return 0;
}

C#实现：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Xml;
using static System.Console;

namespace ConsoleApp1
{

    public abstract class Beverage
    {
        public String description = "Unkonw Beverage";
        virtual public String getDescription()
        {
            return description;
        }
        public abstract double cost();
    }
    public abstract class ComdimentDecorator :Beverage
    {
        
    }
    public class Espresso : Beverage
    {
        public Espresso()
        {
            description = "Espressp Coffee";
        }
        public override double cost()
        {
            return 1.99;
        }
    }
    public class HouseBlend : Beverage
    {
        public HouseBlend()
        {
            description = "House Blend Coffee";
        }
        public override double cost()
        {
            return 0.89;
        }
    }
    public class DarkRoast : Beverage
    {
        public DarkRoast()
        {
            description = "Dark Roast Coffee";
        }
        public override double cost()
        {
            return 0.99;
        }
    }
    public class Decaf : Beverage
    {
        public Decaf()
        {
            description = "Decaf Coffee";
        }
        public override double cost()
        {
            return 1.05;
        }
    }
    public class Mocha : ComdimentDecorator
    {
        Beverage beverage;
        public Mocha(Beverage beverage)
        {
            this.beverage = beverage;
        }
        public override double cost()
        {
            return this.beverage.cost()+0.2;
        }

        public override string getDescription()
        {
            return this.beverage.getDescription() + ", Mocha";
        }
    }
    public class Milk : ComdimentDecorator
    {
        Beverage beverage;
        public Milk(Beverage beverage)
        {
            this.beverage = beverage;
        }
        public override double cost()
        {
            return this.beverage.cost() + 0.1;
        }

        public override string getDescription()
        {
            return this.beverage.getDescription() + ", Milk";
        }
    }
    public class Soy : ComdimentDecorator
    {
        Beverage beverage;
        public Soy(Beverage beverage)
        {
            this.beverage = beverage;
        }
        public override double cost()
        {
            return this.beverage.cost() + 0.15;
        }

        public override string getDescription()
        {
            return this.beverage.getDescription() + ", Soy";
        }
    }
    public class Whip : ComdimentDecorator
    {
        Beverage beverage;
        public Whip(Beverage beverage)
        {
            this.beverage = beverage;
        }
        public override double cost()
        {
            return this.beverage.cost() + 0.1;
        }

        public override string getDescription()
        {
            return this.beverage.getDescription() + ", Whip";
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            Beverage beverage = new Espresso();
            WriteLine(beverage.getDescription() + "\n" + beverage.cost()+"\n");

            Beverage beverage2 = new DarkRoast();
            beverage2 = new Mocha(beverage2);
            beverage2 = new Mocha(beverage2);
            beverage2 = new Whip(beverage2);
            WriteLine(beverage2.getDescription() + "\n" + beverage2.cost()+"\n");

            Beverage beverage3 = new HouseBlend();
            beverage3 = new Soy(beverage3);
            beverage3 = new Mocha(beverage3);
            beverage3 = new Whip(beverage3);
            WriteLine(beverage3.getDescription() + "\n" + beverage3.cost()+"\n");
        }
    }
}