visitor.h
/************************************************************************ 
 * description: 为该对象结构中ConcreteElement的每一个类声明一个visit操作 
 * remark:  
************************************************************************/ 
#ifndef _VISITOR_H_ 
#define _VISITOR_H_ 
class concreteElementA; 
class concreteElementB; 
class visitor 
{ 
public: 
 visitor(){}; 
 virtual ~visitor(){}; 
 virtual void visitConcreteElementA(concreteElementA* pConcreteElementA) = 0; 
 virtual void visitConcreteElementB(concreteElementB* pConcreteElementB) = 0; 
}; 
#endif// _VISITOR_H_ 

/************************************************************************ 
 * description: 具体访问者，实现每个由visitor声明的操作。每个操作实现算法 
    的一部分，而该算法片断乃是对应于结构中对象的类 
 * remark:  
************************************************************************/ 
#ifndef _CONCRETE_VISITOR_H_ 
#define _CONCRETE_VISITOR_H_ 
#include "visitor.h" 
#include <iostream> 
using namespace std; 
class concreteVisitor1 : public visitor 
{ 
public: 
 concreteVisitor1(){}; 
 ~concreteVisitor1(){}; 
 virtual void visitConcreteElementA(concreteElementA* pConcreteElementA) 
 { 
  cout << "concreteElementA被concreteVisitor1访问" << endl;  
 } 
 virtual void visitConcreteElementB(concreteElementB* pConcreteElementB) 
 { 
  cout << "concreteElementB被concreteVisitor1访问" << endl;   
 } 
}; 
 
class concreteVisitor2 : public visitor 
{ 
public: 
 concreteVisitor2(){}; 
 ~concreteVisitor2(){}; 
 virtual void visitConcreteElementA(concreteElementA* pConcreteElementA) 
 { 
  cout << "concreteElementA被concreteVisitor2访问" << endl;  
 } 
 virtual void visitConcreteElementB(concreteElementB* pConcreteElementB) 
 { 
  cout << "concreteElementB被concreteVisitor2访问" << endl;   
 } 
}; 
#endif// _CONCRETE_VISITOR_H_ 

/************************************************************************ 
 * description: 定义一个accept操作，它以一个访问者为参数 
 * remark:  
************************************************************************/ 
#ifndef _ELEMENT_H_ 
#define _ELEMENT_H_ 
class visitor; 
class element 
{ 
public: 
 element(){}; 
 virtual ~element(){}; 
 virtual void accept(visitor* pVisitor) = 0; 
}; 
#endif// _ELEMENT_H_ 

#ifndef _CONCRETE_ELEMENT_H_ 
#define _CONCRETE_ELEMENT_H_ 
#include "element.h" 
#include <iostream> 
using namespace std; 
class concreteElementA : public element 
{ 
public: 
 concreteElementA(){}; 
 ~concreteElementA(){}; 
 // 充分利用双分派技术，实现处理与数据结构的分离 
 virtual void accept(visitor* pVisitor) 
 { 
  if (NULL != pVisitor) 
  { 
   pVisitor->visitConcreteElementA(this); 
  } 
 } 
 // 其他的相关方法 
 void operationA() 
 { 
  cout << "具体元素A的其他相关方法" << endl; 
 } 
}; 
class concreteElementB : public element 
{ 
public: 
 concreteElementB(){}; 
 ~concreteElementB(){}; 
 // 充分利用双分派技术，实现处理与数据结构的分离 
 virtual void accept(visitor* pVisitor) 
 { 
  if (NULL != pVisitor) 
  { 
   pVisitor->visitConcreteElementB(this); 
  } 
 } 
 // 其他的相关方法 
 void operationB() 
 { 
  cout << "具体元素B的其他相关方法" << endl; 
 } 
}; 
#endif// _CONCRETE_ELEMENT_H_ 

/************************************************************************ 
 * description: 枚举元素，可以提供一个高层的接口以允许访问者访问它的元素 
 * remark:  
************************************************************************/ 
#ifndef _OBJECT_STRUCTURE_H_ 
#define _OBJECT_STRUCTURE_H_ 
#include "element.h" 
#include "visitor.h" 
#include <list> 
using namespace std; 
class objectStructure 
{ 
public: 
 void attach(element* pElement) 
 { 
  m_list.push_back(pElement); 
 } 
 void detach(element* pElement) 
 { 
  m_list.remove(pElement); 
 } 
 void accept(visitor* pVisitor) 
 { 
  list<element*>::iterator Iter; 
  for (Iter = m_list.begin(); Iter != m_list.end(); ++Iter) 
  { 
   if (NULL != *Iter) 
   { 
    (*Iter)->accept(pVisitor); 
   }    
  } 
 } 
private: 
 list<element*> m_list; 
}; 
#endif// _OBJECT_STRUCTURE_H_ 

// visitorApp.cpp : 定义控制台应用程序的入口点。 
// 
#include "stdafx.h" 
#include "objectStructure.h" 
#include "concreteElement.h" 
#include "concreteVisitor.h" 
void freePtr(void* vptr) 
{ 
 if (NULL != vptr) 
 { 
  delete vptr; 
  vptr = NULL; 
 } 
} 
int _tmain(int argc, _TCHAR* argv[]) 
{ 
 objectStructure* pObject = new objectStructure(); 
 if (NULL != pObject) 
 { 
  element* pElementA = new concreteElementA(); 
  element* pElementB = new concreteElementB(); 
  pObject->attach(pElementA); 
  pObject->attach(pElementB); 
  concreteVisitor1* pVisitor1 = NULL; 
  pVisitor1 = new concreteVisitor1(); 
  concreteVisitor2* pVisitor2 = NULL; 
  pVisitor2 = new concreteVisitor2(); 
  pObject->accept(pVisitor1); 
  pObject->accept(pVisitor2); 
  system("pause"); 
  freePtr(pVisitor2); 
  freePtr(pVisitor1); 
  freePtr(pElementB); 
  freePtr(pElementA); 
  freePtr(pObject); 
 } 
 return 0; 
}