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