访问者模式——C++实现

问题描述：

 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++源代码：

 

#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("小明");
	visitor2->setName("小张");
	visitor3->setName("小王");
	
	
	basket->accept(visitor1);	
	basket->accept(visitor3);
	basket->accept(visitor2);

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

　　

运行结果：