Visitor (C++实现）

// Visitor.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include <iostream>
#include <string>

using namespace std;

class Visitor;

class Element
{
public:
 virtual ~Element(){}

 virtual void Accept(Visitor &rVisitor) = 0;

protected:
 Element(){}
};

class ConcreateElementA
 : public Element
{
public:
  ConcreateElementA(string s):state_A(s)
  {

  }
 virtual ~ConcreateElementA() {}

 virtual void Accept(Visitor &rVisitor);

 string getState()
 {
  return state_A;
 }

private:
 string state_A;
 
};

class ConcreateElementB
 : public Element
{
public:
 ConcreateElementB(string s): state_B(s)
 {
 }

 virtual void Accept(Visitor &rVisitor);
 string getState()
 {
  return state_B;
 }
private:
 string state_B;
};

class Visitor
{
public:
 virtual ~Visitor(){}

 virtual void VisitConcreateElementA(ConcreateElementA *pConcreateElementA) = 0;
 virtual void VisitConcreateElementB(ConcreateElementB *pConcreateElementB) = 0;

protected:
 Visitor(){}
};

class ConcreateVisitorA
 : public Visitor
{
public:
 virtual ~ConcreateVisitorA(){}

 virtual void VisitConcreateElementA(ConcreateElementA *pConcreateElementA)
 {
  cout<<"+++++"<<pConcreateElementA->getState()<<"+++++"<<endl;
 }
 virtual void VisitConcreateElementB(ConcreateElementB *pConcreateElementB)
 {
  cout<<"-----"<<pConcreateElementB->getState()<<"-----"<<endl;
 }
};

class ConcreateVisitorB
 : public Visitor
{
public:
 virtual ~ConcreateVisitorB(){}

 virtual void VisitConcreateElementA(ConcreateElementA *pConcreateElementA)
 {
  cout<<"@@@@@"<<pConcreateElementA->getState()+""<<"@@@@@"<<endl;
 }
 virtual void VisitConcreateElementB(ConcreateElementB *pConcreateElementB)
 {
  cout<<"#####"<<pConcreateElementB->getState()<<"#####"<<endl;
 }
};

void ConcreateElementA::Accept(Visitor &rVisitor)
{
 rVisitor.VisitConcreateElementA(this);
}

void ConcreateElementB::Accept(Visitor &rVisitor)
{
 rVisitor.VisitConcreateElementB(this);
}

int _tmain(int argc, _TCHAR* argv[])
{
 Visitor *pVisitorA = new ConcreateVisitorA();
 Visitor *pVisitorB= new ConcreateVisitorB();
 Element *pElement  = new ConcreateElementA(string("XXXXX"));

 pElement->Accept(*pVisitorA);
 pElement->Accept(*pVisitorB);

 Element *pElement2  = new ConcreateElementB(string("YYYYY"));

 pElement2->Accept(*pVisitorA);
 pElement2->Accept(*pVisitorB);

 delete pElement;
 delete pElement2;
 delete pVisitorA;
 delete pVisitorB;

 return 0;
}