工厂方法模式C++实现

工厂方法模式：定义一个用于创建对象的接口，让子类决定实例化哪一个类；工厂方法将一个类的实例化延迟到其子类；

工厂模式实现时，由客户端决定实例化哪一个具体类来实现运算类；即工厂方法把简单工厂的内部判断逻辑延迟到客户端代码来运行；

与简单工厂模式对比：工厂模式克服了简单工厂模式违背了开放-封闭原则的缺点，又保持了封装对象创建过程的优点；

工厂模式UML类图：

工厂模式示例：学雷锋

产品抽象类及具体子类、工厂抽象类及其具体子类的接口：

#ifndef FACTORY_H
#define FACTORY_H
#include <iostream>
#include <string>
using namespace std;

//产品抽象类及具体子类
class LeiFeng
{
public: 
	virtual void swap(){cout << "swap ";}
	virtual void wash(){cout << "wash ";}
	virtual void buyrice(){cout << "buyrice ";}

};
class Undergraduate:public LeiFeng
{
	void swap(){cout << "Undergraduate swap" << endl;}
	void wash(){cout << "Undergraduate wash"<< endl;}
	void buyrice(){cout << "Undergraduate buyrice"<< endl;}
};
class Voluteer:public LeiFeng
{
	void swap(){cout << "Voluteer swap"<< endl;}
	void wash(){cout << "Voluteer wash"<< endl;}
	void buyrice(){cout << "Voluteer buyrice"<< endl;}
};
//抽象工厂及具体工厂子类
class IFactory
{
public:
	virtual LeiFeng *createLeiFeng()=0;
};
class UndergraduateFactory:public IFactory
{
public:
	LeiFeng *createLeiFeng()
	{
		cout << "UndergraduateFactory:" << endl;
		return new Undergraduate();
	}
};
class VoluteerFactory:public IFactory
{
public:
	LeiFeng *createLeiFeng()
	{
		cout << "VoluteerFactory:" << endl;
		return new Voluteer();
	}
};
#endif

客户端代码：

#include "factory.h"

int main()
{
	//大学生雷锋工厂
	IFactory *factory1 = new UndergraduateFactory();
	LeiFeng *std = factory1->createLeiFeng();

	std->swap();
	std->wash();
	std->buyrice();

	cout << endl;
	//志愿者雷锋工厂
	IFactory *factory2 = new VoluteerFactory();
	LeiFeng *vol = factory2->createLeiFeng();

	vol->swap();
	vol->wash();
	vol->buyrice();

	return 0;
}

代码输出为：