设计模式 - 简单工厂模式（C++）

一.简单工厂模式又称静态工厂方法模式（Static Factory Method），它不是Gof 所讲的23种设计模式之一，但是它却是我们在编码过程中经常使用的方法之一。

 

1.静态工厂方法统一管理对象的创建。
静态工厂方法通过传入的参数判断决定创建哪一个产品的实例，封装了对象的创建，客户端只管消费，实现了对责任（模块）的分割。

2.静态工厂方法推迟了产品的实例化。
通过XML配置文件就能改变具体要创建的产品实例，修改为其它的产品实例，代码不须重新编译。

classFile.h

#pragma once
class basicObject
{
public:
	basicObject(void);
	~basicObject(void);
	
	virtual int operation_function(int a,int b);
	
private:
	int tempa;
	int tempb;
};
class addObject : public basicObject
{
public:
	addObject(void){};
	~addObject(void){};
	virtual int operation_function(int a,int b);
};
class subObject : public basicObject
{
public:
	subObject(void){};
	~subObject(void){};
	virtual int operation_function(int a,int b);
};
class mulObject : public basicObject
{
public:
	mulObject(){};
	~mulObject(){};
	virtual int operation_function(int a,int b);
};
class divObject : public basicObject
{
public:
	divObject(){};
	~divObject(){};
	virtual int operation_function(int a,int b);
};
class tochObject : public basicObject
{
public:
	tochObject(){};
	~tochObject(){};
	virtual int operation_function(int a,int b);
};
class ArithOperatorFactory
{
public:
	ArithOperatorFactory(){};
	~ArithOperatorFactory(){};
	basicObject* CreateArithOperator(const char chsrc);
};

classFile.cpp
#include "StdAfx.h"
#include "classFile.h"
basicObject::basicObject(void) : 
tempa(0),
tempb(0)
{
}
basicObject::~basicObject(void)
{
}
int basicObject::operation_function(int a,int b)
{
	return 0;
}

int addObject::operation_function(int a,int b)
{
	return a + b;
}

int subObject::operation_function(int a,int b)
{
	return a - b;
}

int mulObject::operation_function(int a,int b)
{
	return a * b;
}

int divObject::operation_function(int a,int b)
{
	return a / b;
}


int tochObject::operation_function(int a,int b)
{
	return a % b;
}

basicObject * ArithOperatorFactory::CreateArithOperator(const char chsrc)
{
	basicObject *obj;
	switch(chsrc)
	{
	case '+':
		obj = new addObject;
		break;
	case '-':
		obj = new subObject;
		break;
	case '*':
		obj = new mulObject;
		break;
	case '/':
		obj = new divObject;
		break;
	case '%':
		obj = new tochObject;
		break;
	default:
		obj = NULL;
		break;
	}
	return obj;
}

main.cpp
#include "classFile.h"
#include <iostream>
#include <stdlib.h>
using namespace std;
int _tmain(int argc, _TCHAR* argv[])
{
	ArithOperatorFactory * factoryObj = new ArithOperatorFactory;
	basicObject * addObj = factoryObj->CreateArithOperator('+');
	if (addObj == NULL)
	{
		return 0;
	}
	int k = addObj->operation_function(20, 30);
	cout << "k = " << k << endl;
	system("pause");
	return 0;
}