策略模式

策略模式定义了一系列的算法，并将每一个算法封装起来，而且使它们还可以相互替换。从这些类中抽象出公共接口。策略模式让算法独立于使用它的客户而独立变化。

//图书折扣策略的抽象类
class CBookStrategy
{
public:
	virtual double GetDiscount()=0;
	CBookStrategy()
	{
	
	}
};
//无折扣
class CNonDiscount: public CBookStrategy
{
private:
	int     m_BookCount;
	double  m_BookPrice;
public:
	CNonDiscount(int BookCount,double BookPrice)
	{
		m_BookCount = BookCount;
		m_BookPrice = BookPrice;
	}
	virtual double GetDiscount()
	{
		return m_BookCount*m_BookPrice;
	}
};

//按百分比折扣
class CPerDiscount : public CBookStrategy
{
private:
	int     m_BookCount;
	double  m_BookPrice;
	double  m_Percent;
public:
	double GetPercent()
	{
		return m_Percent;
	}
	void SetPercent(double Percent)
	{
		m_Percent = Percent;
	}
	
	CPerDiscount(int BookCount,double BookPrice,double Percent)
	{
		m_BookCount = BookCount;
		m_BookPrice = BookPrice;
		m_Percent   = Percent;
	}
	virtual double GetDiscount()
	{
		return m_BookCount*m_BookPrice*m_Percent;
	}
};
//按具体价格折扣
class CPriceDiscount: public CBookStrategy
{
private:
	int     m_BookCount;
	double  m_BookPrice;
	double  m_DiscountPrice;
public:
	double GetDiscountPrice()
	{
		return m_DiscountPrice;
	}
	void SetPercent(double Price)
	{
		m_DiscountPrice = Price;
	}
	virtual double GetDiscount()
	{
		return m_BookCount*m_DiscountPrice;
	}
	CPriceDiscount(int BookCount,double BookPrice,double DiscountPrice)
	{
		m_BookCount = BookCount;
		m_BookPrice = BookPrice;
		m_DiscountPrice   = DiscountPrice;		
	}
};

int main(int argc, char* argv[])
{

	CBookStrategy* pStrategy;
	//无折扣

	pStrategy = new CNonDiscount(2,35);
	cout << pStrategy->GetDiscount() << '\n';
	delete pStrategy;
	//百分比折扣
	pStrategy = new CPerDiscount(2,35,0.85);
	cout << pStrategy->GetDiscount()<< '\n';
	delete pStrategy;
	//具体价格折扣
	pStrategy = new CPriceDiscount(2,35,33);
	cout <<
		pStrategy->GetDiscount() << '\n';
	delete pStrategy;

	return 0;
}