大话设计模式C++版——简单工厂模式

简单工厂模式应该是所有设计模式中最简单，也最基础的一种模式，以下是一个简单的采用工厂模式写一个加减法的计算器。

1、抽象接口类——依赖倒转原则（高层和底层都要依赖于抽象，针对接口编程）

class IOperation
{
public:
	IOperation() : m_nNuml(0), m_nNumr(0) {}
	virtual	~IOperation() {}
	
	virtual	void	SetNum(int nNuml = 0, int nNumr = 0)
	{
		m_nNuml = nNuml;
		m_nNumr = nNumr;
	}
	virtual	int		CalculateResult() = 0;
	
protected:
	int	m_nNuml, m_nNumr;
};

注：m_nNuml, m_nNumr申明为protected，是为了让继承类中能够使用，同时又保持其访问的私有性，这和C#是不一样的地方

2、接口实现对象类——加法、减法类（乘除法就省略了，类似）

class COperation_Add : public IOperation
{
public:
	int		CalculateResult()
	{
		return	m_nNuml + m_nNumr;
	}
};


class COperation_Dec : public IOperation
{
public:
	int		CalculateResult()
	{
		return	m_nNuml - m_nNumr;
	}
};

<span style="font-size:14px;">class CClassFactory
{
public:
	CClassFactory() {}
	~CClassFactory() {}
	
	IOperation*	CreateObject(char cOperation)
	{
		IOperation*	poCOperation = NULL;
		switch (cOperation)
		{
		case '+':
			{
				poCOperation = new COperation_Add();
				break;
			}
		case '-':
			{
				poCOperation = new	COperation_Dec();
				break;
			}
			break;
		}
		
		return	poCOperation;
	}
};

void	Test()
{
	CClassFactory	oCClassFactory;
	IOperation*		poIOperation = NULL;

	poIOperation = oCClassFactory.CreateObject('+');
	
	if (poIOperation)
	{
		poIOperation->SetNum(2, 3);
		printf("2 + 3 = %d\n", poIOperation->CalculateResult());
		
		delete poIOperation;
	}
}

大话设计模式C++版——简单工厂模式

原文：http://blog.csdn.net/gufeng99/article/details/45932177