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目录

基本概念

工厂方法模式（Factory Method）：定义一个用于创建对象的接口，让字类决定实例化哪一个类。工厂方法使一个类的实例化延迟到其子类；

简单工厂模式的最大优点在用户工厂类中包含了必要的逻辑判断，根据客户端的选择条件动态实例化相关的类，对于客户端来说，去除了具体产品的依赖。

工厂方法模式实现时，客户端需要决定实例化哪一个工厂来实现运算类，选择判断的问题还是存在的，也就是说，工厂方法把简单工厂内部逻辑判断移到了客户端代码来进行。

UML图如下（这里以计算器为例）

代码及实例

程序运行截图如下：

源码如下：

Head.h

#ifndef HEAD_H#define HEAD_H//运算相关class Operation{public:	double m_numberA;	double m_numberB;	virtual double getResult();};class AddOperation: public Operation{public:	AddOperation();	double getResult();};class MultiOperation: public Operation{public:	MultiOperation();	double getResult();};//工厂相关class IFactory{public:	virtual Operation *createOperation();};class AddFactory: public IFactory{public:	Operation *createOperation();};class MultiFactory: public IFactory{public:	Operation *createOperation();};                                                                                                                                                                                                                                                         #endif	//HEAD_H

Head.cpp

#include "Head.h"#include 
   
    #include 
    
     using namespace std;Operation *IFactory::createOperation(){	return nullptr;}Operation *AddFactory::createOperation(){	return new AddOperation;}double Operation::getResult(){	return -1;}AddOperation::AddOperation(){	m_numberA = 0.0;	m_numberB = 0.0;}double AddOperation::getResult(){	return m_numberA + m_numberB;}MultiOperation::MultiOperation(){	m_numberA = 0.0;	m_numberB = 0.0;}double MultiOperation::getResult(){	return m_numberA * m_numberB;}Operation * MultiFactory::createOperation(){	return new MultiOperation;}
    
   

main.cpp

#include "Head.h"#include 
   
    using namespace std;int main(int *argc, int *argv){	IFactory *operAddFactory = new AddFactory;	Operation *addOper = operAddFactory->createOperation();	addOper->m_numberA = 100;	addOper->m_numberB = 200;	cout << "operAddFactory result is : " << addOper->getResult() << endl;	delete operAddFactory;	delete addOper;	cout << "--------------- 华丽的分割线 ---------------" << endl;	IFactory *operMultiFactory = new MultiFactory;	Operation *multiOper = operMultiFactory->createOperation();	multiOper->m_numberA = 12;	multiOper->m_numberB = 5;	cout << "operMultiFactory result is : " << multiOper->getResult() << endl;	delete operMultiFactory;	delete multiOper;	getchar();	return 0;}
   

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