C++设计模式-工厂模式

目录

 

 

基本概念

代码及实例

---

 

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;
}