25.访问者模式

[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。

代码

java

Apple.java

package test25;

public class Apple implements Product {
    @Override
    public void accept(Visitor visitor) {
        visitor.visit(this);
    }
}

Book.java

package test25;

public class Book implements Product{
    @Override
    public void accept(Visitor visitor) {
        visitor.visit(this);
    }
}

BuyBasket.java

package test25;

import java.util.ArrayList;
import java.util.Iterator;

public class BuyBasket{

    private ArrayList list = new ArrayList();

    public void accept(Visitor visitor){
        Iterator iterator = list.iterator();
        while (iterator.hasNext()){
            ((Product)iterator.next()).accept(visitor);
        }
    }

    public void addProduce(Product product){
        list.add(product);
    }

    public void removeProduce(Product product){
        list.remove(product);
    }

}

Client.java

package test25;

public class Client {

    public static void main(String[] args) {
        Product b1 = new Book();
        Product b2 = new Book();
        Product a1 = new Apple();
        Visitor visitor;

        BuyBasket basket = new BuyBasket();
        basket.addProduce(b1);
        basket.addProduce(b2);
        basket.addProduce(a1);

        visitor = new Packager();
        visitor.setName("张三");
        basket.accept(visitor);
    }

}

Customer.java

package test25;

public class Customer extends Visitor{
    @Override
    public void visit(Apple apple) {
        System.out.println("顾客"+name+"选苹果");
    }

    @Override
    public void visit(Book book) {
        System.out.println("顾客"+name+"买书");
    }
}

Packager.java

package test25;

public class Packager extends Visitor{
    @Override
    public void visit(Apple apple) {
        System.out.println("打包员"+name+"打包苹果");
    }

    @Override
    public void visit(Book book) {
        System.out.println("打包员"+name+"打包书籍");
    }
}

Product.java

package test25;

public interface Product {

    void accept(Visitor visitor);

}

Saler.java

package test25;

public class Saler extends Visitor{
    @Override
    public void visit(Apple apple) {
        System.out.println("收银员"+
                name+"给苹果过称，计算价格");
    }

    @Override
    public void visit(Book book) {
        System.out.println("收银员"+name+"直接计算书的价格");
    }
}

Visitor.java

package test25;

public abstract class Visitor {

    protected String name;
    public void setName(String name){
        this.name = name;
    }

    public abstract void visit(Apple apple);
    public abstract void visit(Book book);

}

C++代码

#include <iostream>
#include <vector>
#include <string>
using namespace std;

class Visitor;
class Apple;
class Book;
//抽象产品类
class Product{
public:
    virtual void accept(Visitor *visitor){};
};

//抽像访问者
class Visitor{
protected:
    string name;
public:
    void setName(string name){
        this->name = name;
    }
    virtual void visit(Apple *apple){}
    virtual void visit(Book *book){}
};
class Packager:public Visitor{
public:
    void visit(Apple *apple) override {
        cout<<"打包员"+name+"打包苹果"<<endl;
    }
    void visit(Book *book) override {
        cout<<"打包员"+name+"打包书籍"<<endl;
    }
};
//具体产品类Apple
class Apple: public Product{
public:
    void accept(Visitor *visitor){
        visitor->visit(this);
    }
};
//具体产品类Book
class Book:public Product{
public:
    void accept(Visitor *visitor){
        visitor->visit(this);
    }
};
//购物车类BuyBasket
class BuyBasket{
private:
    vector<Product*> list;
public:
    void accept(Visitor *visitor){
//        vector<Product>::iterator i;
//        for (i = list.begin(); i != list.end(); ++i) {  //用迭代器遍历容器
//            i->accept(visitor);
//        }
        for(int i=0;i<list.size();i++){
            list[i]->accept(visitor);
        }
    }
    void addProduce(Product *product){
        list.push_back(product);
    }
};

int main(){
    Book *b1 = new Book();
    Book *b2 = new Book();
    Apple *a1 = new Apple();
    Packager *visitor = new Packager();

    BuyBasket basket;
    basket.addProduce(b1);
    basket.addProduce(b2);
    basket.addProduce(a1);

    string name = "abc";
    visitor->setName(name);
    basket.accept(visitor);
}