学步园

#include <iostream>
#include <list>
using namespace std;

//
struct IElement;

struct IVisitor
{
public:
	virtual ~IVisitor() { }

	virtual void VisitFood(IElement *pElement) = 0;
	virtual void VisitDrink(IElement *pElement) = 0;
};

struct IElement
{
public:
	IElement(string name) : m_name(name) { }
	virtual ~IElement() { }

	virtual void Accept(IVisitor *pVisitor) = 0;

	string getName() { return m_name; }

private:
	string m_name;
};

//
class CCashier : public IVisitor
{
public:
	virtual ~CCashier() { }
	
	virtual void VisitFood(IElement *pElement) { cout<<"Cashier visit "<<pElement->getName().c_str()<<endl; }
	virtual void VisitDrink(IElement *pElement) { cout<<"Cashier visit "<<pElement->getName().c_str()<<endl; }
};

class CBuyer : public IVisitor
{
public:
	virtual ~CBuyer() { }

	virtual void VisitFood(IElement *pElement) { cout<<"Buyer visit "<<pElement->getName().c_str()<<endl; }
	virtual void VisitDrink(IElement *pElement) { cout<<"Buyer visit "<<pElement->getName().c_str()<<endl; }
};

//
class CFood : public IElement
{
public:
	CFood(string name) : IElement(name) { }
	virtual ~CFood() { }

	virtual void Accept(IVisitor *pVisitor) { pVisitor->VisitFood(this); }
};

class CDrink : public IElement
{
public:
	CDrink(string name) : IElement(name) { }
	virtual ~CDrink() { }

	virtual void Accept(IVisitor *pVisitor) { pVisitor->VisitDrink(this); }
};

//
class CObjects
{
public:

	void Add(IElement *pElement) { m_pElementList.push_back(pElement); }
	void Remove(IElement *pElement) { m_pElementList.remove(pElement); }

	void Accept(IVisitor *pVisitor)
	{
		list<IElement*>::iterator ite = m_pElementList.begin();
		for(; m_pElementList.end() != ite; ite++)
		{
			(*ite)->Accept(pVisitor);
		}
	}

private:
	list<IElement*> m_pElementList;
};

//
void main()
{
	CObjects objects;

	CFood food("Food");
	CDrink drink("drink");
	objects.Add(&food);
	objects.Add(&drink);

	CCashier cashier;
	objects.Accept(&cashier);

	CBuyer buyer;
	objects.Accept(&buyer);
}