简单工厂模式的工厂类一般是使用静态方法，通过接收的参数的不同来返回不同的对象实例。
不修改代码的话，是无法扩展的。
#include <iostream>
using namespace std;
class COperation
{
public:
int m_nFirst;
int m_nSecond;
virtual double GetResult()
{
double dResult = 0;
return dResult;
}
};
//加法
class AddOperation: public COperation
{
virtual double GetResult()
{
return m_nFirst+ m_nSecond;
}
};
//减法
class SubOperation: public COperation
{
public:
virtual double GetResult()
{
return m_nFirst - m_nSecond;
}
};//工厂类
class CCaculatorFactory
{
public:
static COperation * Create(char cOperator);
};
COperation * CCaculatorFactory::Create(char cOperator)
{
COperation * oper;
switch(cOperator)
{
case '+':
oper = new AddOperation();
break;
case '-':
oper = new SubOperation();
break;
default:
oper = new AddOperation();
break;
}
return oper;
}int _tmain(int argc, _TCHAR * argv [])
{
int a, b;
cin >> a >> b;
COperation * op = CCaculatorFactory::Create('-');
op->m_nFirst = a;
op->m_nSecond = b;
cout << op->GetResult() << endl;
return 0;
}
原文：http://blog.csdn.net/lightupheaven/article/details/38823067