11.1

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. 画出对应的类图；

 

2. 提交源代码；

from abc import ABC, abstractmethod
from typing import List


# 抽象访问者类
class Visitor(ABC):
    @abstractmethod
    def visitBook(self, book):
        pass

    @abstractmethod
    def visitElectronics(self, electronics):
        pass

    @abstractmethod
    def visitClothes(self, clothes):
        pass

    # 新增的访问购物车的抽象方法
    @abstractmethod
    def visitShoppingCart(self, shoppingCart):
        pass


# 购物车类
class ShoppingCart:
    def __init__(self):
        self.items = []

    def addItem(self, item):
        self.items.append(item)

    def removeItem(self, item):
        self.items.remove(item)

    def accept(self, visitor):
        visitor.visitShoppingCart(self)
        for item in self.items:
            item.accept(visitor)


# 抽象商品类
class Item(ABC):
    def __init__(self, name, price):
        self.name = name
        self.price = price

    @abstractmethod
    def accept(self, visitor):
        pass

    def getName(self):
        return self.name

    def getPrice(self):
        return self.price


# 书籍类
class Book(Item):
    def __init__(self, name, price, author):
        super().__init__(name, price)
        self.author = author

    def accept(self, visitor):
        visitor.visitBook(self)

    def getAuthor(self):
        return self.author


# 电子产品类
class Electronics(Item):
    def __init__(self, name, price, brand):
        super().__init__(name, price)
        self.brand = brand

    def accept(self, visitor):
        visitor.visitElectronics(self)

    def getBrand(self):
        return self.brand


# 衣服类
class Clothes(Item):
    def __init__(self, name, price, size, color):
        super().__init__(name, price)
        self.size = size
        self.color = color

    def accept(self, visitor):
        visitor.visitClothes(self)

    def getSize(self):
        return self.size

    def getColor(self):
        return self.color


# 打包员类（具体访问者）
class Packer(Visitor):
    def visitBook(self, book):
        print(f"正在打包书籍：{book.getName()}，作者：{book.getAuthor()}")

    def visitElectronics(self, electronics):
        print(f"正在打包电子产品：{electronics.getName()}，品牌：{electronics.getBrand()}")

    def visitClothes(self, clothes):
        print(f"正在打包衣服：{clothes.getName()}，尺寸：{clothes.getSize()}，颜色：{clothes.getColor()}")

    def visitShoppingCart(self, shoppingCart):
        print("开始打包购物车中的商品...")
        for item in shoppingCart.items:
            item.accept(self)


if __name__ == "__main__":
    shopping_cart = ShoppingCart()

    book = Book("Python从入门到实践", 89.0, "Eric Matthes")
    electronics = Electronics("iPhone 14", 7999.0, "Apple")
    clothes = Clothes("T恤", 99.0, "M", "白色")

    shopping_cart.addItem(book)
    shopping_cart.addItem(electronics)
    shopping_cart.addItem(clothes)

    packer = Packer()
    shopping_cart.accept(packer)

 

3. 注意编程规范。