实验 25：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。
实验要求：
1.提交源代码，不要提交类图；
Java代码
package org.example.fwz;
public abstract class AbstractGoods implements Goods{
private String name;
private int num;
private int price;
public AbstractGoods(String name, int num,int price) {
this.name = name;
this.num = num;
this.price = price;
}
@Override
public abstract int accept(Visitor visitor);
public String getName() {
return name;
}
public int getNum() {
return num;
}
public int getPrice() {
return price;
}
}
package org.example.fwz;
public class Book extends AbstractGoods {
public Book(String name, int num, int price) {
super(name, num, price);
}
@Override
public int accept(Visitor visitor) {
return visitor.visit(this);
}
}
package org.example.fwz;
public class Client {
public static void main(String[] args) {
Shoppingcar shoppingCar = new Shoppingcar();
shoppingCar.add(new Book("西游记", 2, 25));
shoppingCar.add(new Book("活着", 2, 30));
shoppingCar.add(new Fruit("苹果", 2, 5));
shoppingCar.add(new Fruit("火龙果", 6, 8));
shoppingCar.getCosts();
}
}
package org.example.fwz;
public class Fruit extends AbstractGoods {
public Fruit(String name, int num, int price) {
super(name, num, price);
}
@Override
public int accept(Visitor visitor) {
return visitor.visit(this);
}
}
package org.example.fwz;
public interface Goods {
public int accept(Visitor visitor);
public String getName();
public int getNum();
public int getPrice();
}
package org.example.fwz;
import java.util.ArrayList;
import java.util.List;
public class Shoppingcar {
private static final List
private static final Visitor visitor = new shouyinyuan();
public void add(Goods g) {
goods.add(g);
}
public void remove(Goods g) {
goods.remove(g);
}
public int getCosts() {
int sum = 0;
int i = 1;
for (Goods g : goods) {
int c = g.accept(visitor);
System.out.println(g.getName() + "：" + c + "元");
sum = sum + c;
}
System.out.println("一共是：" + sum + " 元");
return sum;
}
}
package org.example.fwz;
public class shouyinyuan implements Visitor {
@Override
public int visit(Book book) {
int cost = book.getNum() * book.getPrice();
return cost;
}
@Override
public int visit(Fruit fruit) {
int cost = fruit.getNum() * fruit.getPrice();
return cost;
}
}
package org.example.fwz;
public interface Visitor {
int visit(Book book) ;
int visit(Fruit fruit);
}
C++代码
include
include
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("小龚");
visitor2->setName("小张");
visitor3->setName("小橘");
basket->accept(visitor1);
basket->accept(visitor3);
basket->accept(visitor2);
delete a1, b1,visitor1, visitor2, visitor3;
return 0;
}
- 注意编程规范。