设计模式18：访问者模式【行为型】

#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);}