实验 25：访问者模式

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++源码：

 

#include<iostream>
#include <list>
using namespace std;
class Apple;
class Book;
//抽象访问者
class Visitor
{
protected:
    string name;
public:
    void setName(string name)
    {
        this->name = name;
    }
    string getname() {
        return name;
    }
    virtual void visit(Apple *apple)=0;
    virtual void visit(Book *book)=0;
};
//抽象元素
class Product
{
public:
    virtual void accept(Visitor *visitor)=0;
};
//具体元素
class Apple :public  Product
{
public:
    void accept(Visitor *visitor)
    {
        visitor->visit(this);
    }
};
//具体元素
class Book :public Product
{
public:
    void accept(Visitor *visitor)
    {
        visitor->visit(this);
    }
};
//对象结构
class BuyBasket
{
private:
    list< Product*> product;
public:
    void accept(Visitor* visitor)
    {
        for (std::list<Product*>::iterator it = product.begin(); it != product.end(); ++it)
            (*it)->accept(visitor);
    }
    void addProduct(Product* product2)
    {
        product.push_back(product2);

    }
    void removeProduct(Product* product2)
    {
        product.remove(product2);
    }
};
class Saler :public Visitor
{
public:
    void visit(Apple *apple)
    {
        cout << "收银员" <<name.c_str() << "给苹果过秤，然后计算其价格。" << endl;
    }
    void visit(Book *book)
    {
        cout << "收银员" << name.c_str() << "直接计算书的价格。" << endl;
    }
};
class Customer :public Visitor
{
public:
    void visit(Apple *apple)
    {
        cout << "顾客" << name.c_str() << "选苹果。" << endl;
    }

    void visit(Book *book)
    {
        cout << "顾客" << name.c_str() << "买书。" << endl;
    }
};
class Pack {
private:
    list< Product*> product;
public:
    void accept(Visitor* visitor)
    {
        for (std::list<Product*>::iterator it = product.begin(); it != product.end(); ++it)
            (*it)->accept(visitor);

    }
    void addProduct(Product* product2)
    {
        product.push_back(product2);

    }
    void removeProduct(Product* product2)
    {
        product.remove(product2);
    }
};

class Packer :public Visitor {
public:
    void visit(Apple *apple) {

        cout << "打包员" << name.c_str() << "给购物车中的苹果进行打包。" << endl;
    }
    void visit(Book *book) {
        cout << "打包员" << name.c_str() << "给购物车中的书本进行打包。" << endl;
    }
};
int  main()
{
    Product *b1 = new Book();
    Product *a1 = new Apple();
    Visitor* visitor1 = new Customer();
    Visitor* visitor2 = new Packer();
    Visitor* visitor3 = new Saler();

    BuyBasket *basket = new BuyBasket();
    basket->addProduct(b1);
    basket->addProduct(a1);

    visitor1->setName("小A");
    visitor2->setName("小B");
    visitor3->setName("小C");


    basket->accept(visitor1);
    basket->accept(visitor3);
    basket->accept(visitor2);

    delete a1, b1,visitor1, visitor2, visitor3;
    return 0;
}