求索阁

#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);
}