Design Pattern Visitor 访问者模式

访问者模式，就是我们已经有一系列的对象了，那么就可以使用一个visitor对象一次性遍历所有的对象，就好像这个visitor访问了所有这些对象一样，所以就叫访问者模式。

实现起来也很简单，就是三个基类，其他类都是这些基类的衍生类。

下面的Action类就是访问者类了，而Person类就是被访问的对象类，而House是一个接待容器，可以接待不同的Action类。

#include <stdio.h>
#include <iostream>
#include <string>
#include <vector>
using namespace std;

class Person;

class Action
{
public:
	string present;
	string gun;
	virtual void drinkBeer(Person *p) = 0;
	virtual void getAGun(Person *p) = 0;
};

class ActionOne:public Action
{
public:
	ActionOne()
	{
		present = "Alcohol";
		gun = "Laiser";
	}
	void drinkBeer(Person *p);
	void getAGun(Person *p);
};

class ActionTwo:public Action
{
public:
	ActionTwo()
	{
		present = "Beer";
		gun = "Machine Gun";
	}
	void getAGun(Person *p);
	void drinkBeer(Person *p);
};

class Person
{	
public:
	string something;
	virtual void receivedVisitor(Action *visitor) = 0;
};

class Bill:public Person
{
public:
	Bill()
	{
		something = "food";
	}
	void receivedVisitor(Action *visitor)
	{
		puts("\nVisitor to Bill bring :");
		puts(visitor->present.c_str());
		visitor->drinkBeer(this);
	}
};

class Mark:public Person
{
public:
	Mark()
	{
		something = "Weapon";
	}
	void receivedVisitor(Action *visitor)
	{
		puts("\nVisitor to Mark bring :");
		puts(visitor->gun.c_str());
		visitor->getAGun(this);
	}
};

void ActionOne::drinkBeer(Person *p)
{
	puts("Let's eat something");
	puts(p->something.c_str());
}

void ActionOne::getAGun(Person *p)
{
	puts("Let's gear up");
	puts(p->something.c_str());
}

void ActionTwo::getAGun(Person *p)
{
	puts("Let's gear up");
	puts(p->something.c_str());
}

void ActionTwo::drinkBeer(Person *p)
{
	puts("Let's eat something");
	puts(p->something.c_str());
}

class House
{
protected:
	vector<Person *> vps;
public:
	void addPerson(Person *p)
	{
		vps.push_back(p);
	}
	void receiver(Action *visitor)
	{
		for (int i = 0; i < (int)vps.size(); i++)
		{
			vps[i]->receivedVisitor(visitor);
		}
	}
	~House()
	{
		for (int i = 0; i < (int)vps.size(); i++)
		{
			delete vps[i];
		}
	}
};

int main()
{
	House house;
	house.addPerson(new Bill);
	house.addPerson(new Mark);
	ActionTwo gun;
	ActionOne drink;
	house.receiver(&gun);
	house.receiver(&drink);
	return 0;
}

Design Pattern Visitor 访问者模式,布布扣,bubuko.com

Design Pattern Visitor 访问者模式

原文：http://blog.csdn.net/kenden23/article/details/37690207