C++设计模式从0进击-1-简单（静态）工厂模式

#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;
}