每日博客

访问者模式

本次实验属于模仿型实验，通过本次实验学生将掌握以下内容：

1、理解访问者模式的动机，掌握该模式的结构；

2、能够利用访问者模式法解决实际问题。

 

 

[实验任务一]：打包员

在我们课堂上的“购物车”的例子中，增加一个新的访问者：打包员，负责对购物车中货物装包。

C++版

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>

class Visitor;
class Element
{
protected:
std::string m_strName;
public:
Element(std::string str)
{
m_strName = str;
}
std::string getName()
{
return m_strName;
}
virtual void Accept(Visitor * visitor) = 0;
};

class ConcreteElementA : public Element
{
public:
ConcreteElementA(std::string str) : Element(str) {}
void Accept(Visitor * visitor);
};

class ConcreteElementB : public Element
{
public:
ConcreteElementB(std::string str) : Element(str) {}
void Accept(Visitor * visitor);
};

class Visitor
{
public:
virtual void VisitConcreteElementA(ConcreteElementA * p) = 0;
virtual void VisitConcreteElementB(ConcreteElementB * p) = 0;
};

class ConcreteVisitorA : public Visitor
{
public:
void VisitConcreteElementA(ConcreteElementA * p)
{
std::cout << "收银员结算" << p->getName() << std::endl;
}
void VisitConcreteElementB(ConcreteElementB * p)
{
std::cout << "收银员结算" << p->getName() << std::endl;
}
};

class ConcreteVisitorB : public Visitor
{
public:
void VisitConcreteElementA(ConcreteElementA * p)
{
std::cout << "打包员打包" << p->getName() << std::endl;
}
void VisitConcreteElementB(ConcreteElementB * p)
{
std::cout << "打包员打包" << p->getName() << std::endl;
}
};

void ConcreteElementA::Accept(Visitor * visitor)
{
visitor->VisitConcreteElementA(this);
}
void ConcreteElementB::Accept(Visitor * visitor)
{
visitor->VisitConcreteElementB(this);
}
class ObjectStructure
{
private:
std::vector<Element *> m_vec;
public:
~ObjectStructure()
{
for (auto it = m_vec.begin(); it != m_vec.end(); it++)
{
delete *it;
}
m_vec.clear();
}
void add(Element * p)
{
m_vec.push_back(p);
}
void accept(Visitor * visitor)
{
for (auto it = m_vec.cbegin(); it != m_vec.cend(); it++)
{
(*it)->Accept(visitor);
}
}
};

int main()
{
using namespace std;
// 访问者模式
ObjectStructure * p = new ObjectStructure();
p->add(new ConcreteElementA("苹果"));
p->add(new ConcreteElementB("书"));

ConcreteVisitorA * pVisitorA = new ConcreteVisitorA();
ConcreteVisitorB * pVisitorB = new ConcreteVisitorB();

p->accept(pVisitorA);
p->accept(pVisitorB);

delete pVisitorA;
delete pVisitorB;
delete p;

getchar();
return 0;
}