visitor模式

#include<iostream>
#include <string>
#include <list>

using namespace std;

class Element;
class Visitor
{
public:
    virtual void Visit(Element *element){};
};

class Element
{
public:
     virtual void Accept(Visitor *visitor){};
};

class Employee:public Element
{
public:
    string name;
	double income;
	int vacationDays;
public:
    Employee(string name,double income,int vacationDays)
	{
	     this->name=name;
		 this->income=income;
		 this->vacationDays=vacationDays;
	}
		
	void Accept(Visitor *visitor)
    {
	    visitor->Visit(this);
	}
};

class IncomeVisitor : public Visitor
{
public:	
	void Visit( Element *element )
	{
		Employee *employee = ((Employee*)element);
		employee->income *= 1.10;
		cout<<employee->name<<" ‘s new income: " <<employee->income<<endl;

	}
};

class VacationVisitor : public Visitor
{
public :
	void Visit( Element *element )
	{
		Employee *employee = ((Employee*)element);
		// Provide 3 extra vacation days
		employee->vacationDays += 3;		
		cout<<employee->name<<" ‘s new vacation days: " <<employee->income<<endl;
	}
}; 	

// "ObjectStructure"		
class Employees
{	
private :
	list< Employee*> employees;

public :
	void Attach( Employee *employee )
	{		
		employees.push_back(employee);		
	}

	void Detach( Employee *employee )
	{
		employees.remove(employee);		
	}

	void Accept( Visitor *visitor )
	{		
		for (std::list<Employee*>::iterator it=employees.begin(); it != employees.end(); ++it)
			(*it)->Accept(visitor);
	}
};		
		
		
void main( )
{
	Employees *e = new Employees();
	e->Attach( new Employee( "Tom", 25000.0, 14 ) );
	e->Attach( new Employee( "Thomas", 35000.0, 16 ) );
	e->Attach( new Employee( "Roy", 45000.0, 21 ) );

	// Create two visitors
	IncomeVisitor *v1 = new IncomeVisitor();
	VacationVisitor *v2 = new VacationVisitor();

	// Employees are visited
	e->Accept( v1 );
	e->Accept( v2 );
}