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抽象工厂

抽象工厂在 Python 中的实现

抽象工厂是一种创建型设计模式 它能创建一系列相关的对象 而无需指定其具体类

抽象工厂定义了用于创建不同产品的接口 但将实际的创建工作留给了具体工厂类 每个工厂类型都对应一个特定的产品变体

在创建产品时 客户端代码调用的是工厂对象的构建方法 而不是直接调用构造函数 new 操作符 由于一个工厂对应一种产品变体 因此它创建的所有产品都可相互兼容

客户端代码仅通过其抽象接口与工厂和产品进行交互 该接口允许同一客户端代码与不同产品进行交互 你只需创建一个具体工厂类并将其传递给客户端代码即可

如果你不清楚工厂 工厂方法抽象工厂模式之间的区别 请参阅工厂模式比较

进一步了解抽象工厂模式

在 Python 中使用模式

复杂度

流行度

使用示例 抽象工厂模式在 Python 代码中很常见 许多框架和程序库会将它作为扩展和自定义其标准组件的一种方式

识别方法 我们可以通过方法来识别该模式——其会返回一个工厂对象 接下来 工厂将被用于创建特定的子组件

概念示例

本例说明了抽象工厂设计模式的结构并重点回答了下面的问题

  • 它由哪些类组成
  • 这些类扮演了哪些角色
  • 模式中的各个元素会以何种方式相互关联

main.py: 概念示例

from __future__ import annotations
from abc import ABC, abstractmethod


class AbstractFactory(ABC):
    """
    The Abstract Factory interface declares a set of methods that return
    different abstract products. These products are called a family and are
    related by a high-level theme or concept. Products of one family are usually
    able to collaborate among themselves. A family of products may have several
    variants, but the products of one variant are incompatible with products of
    another.
    """
    @abstractmethod
    def create_product_a(self) -> AbstractProductA:
        pass

    @abstractmethod
    def create_product_b(self) -> AbstractProductB:
        pass


class ConcreteFactory1(AbstractFactory):
    """
    Concrete Factories produce a family of products that belong to a single
    variant. The factory guarantees that resulting products are compatible. Note
    that signatures of the Concrete Factory's methods return an abstract
    product, while inside the method a concrete product is instantiated.
    """

    def create_product_a(self) -> ConcreteProductA1:
        return ConcreteProductA1()

    def create_product_b(self) -> ConcreteProductB1:
        return ConcreteProductB1()


class ConcreteFactory2(AbstractFactory):
    """
    Each Concrete Factory has a corresponding product variant.
    """

    def create_product_a(self) -> ConcreteProductA2:
        return ConcreteProductA2()

    def create_product_b(self) -> ConcreteProductB2:
        return ConcreteProductB2()


class AbstractProductA(ABC):
    """
    Each distinct product of a product family should have a base interface. All
    variants of the product must implement this interface.
    """

    @abstractmethod
    def useful_function_a(self) -> str:
        pass


"""
Concrete Products are created by corresponding Concrete Factories.
"""


class ConcreteProductA1(AbstractProductA):
    def useful_function_a(self) -> str:
        return "The result of the product A1."


class ConcreteProductA2(AbstractProductA):
    def useful_function_a(self) -> str:
        return "The result of the product A2."


class AbstractProductB(ABC):
    """
    Here's the the base interface of another product. All products can interact
    with each other, but proper interaction is possible only between products of
    the same concrete variant.
    """
    @abstractmethod
    def useful_function_b(self) -> None:
        """
        Product B is able to do its own thing...
        """
        pass

    @abstractmethod
    def another_useful_function_b(self, collaborator: AbstractProductA) -> None:
        """
        ...but it also can collaborate with the ProductA.

        The Abstract Factory makes sure that all products it creates are of the
        same variant and thus, compatible.
        """
        pass


"""
Concrete Products are created by corresponding Concrete Factories.
"""


class ConcreteProductB1(AbstractProductB):
    def useful_function_b(self) -> str:
        return "The result of the product B1."

    """
    The variant, Product B1, is only able to work correctly with the variant,
    Product A1. Nevertheless, it accepts any instance of AbstractProductA as an
    argument.
    """

    def another_useful_function_b(self, collaborator: AbstractProductA) -> str:
        result = collaborator.useful_function_a()
        return f"The result of the B1 collaborating with the ({result})"


class ConcreteProductB2(AbstractProductB):
    def useful_function_b(self) -> str:
        return "The result of the product B2."

    def another_useful_function_b(self, collaborator: AbstractProductA):
        """
        The variant, Product B2, is only able to work correctly with the
        variant, Product A2. Nevertheless, it accepts any instance of
        AbstractProductA as an argument.
        """
        result = collaborator.useful_function_a()
        return f"The result of the B2 collaborating with the ({result})"


def client_code(factory: AbstractFactory) -> None:
    """
    The client code works with factories and products only through abstract
    types: AbstractFactory and AbstractProduct. This lets you pass any factory
    or product subclass to the client code without breaking it.
    """
    product_a = factory.create_product_a()
    product_b = factory.create_product_b()

    print(f"{product_b.useful_function_b()}")
    print(f"{product_b.another_useful_function_b(product_a)}", end="")


if __name__ == "__main__":
    """
    The client code can work with any concrete factory class.
    """
    print("Client: Testing client code with the first factory type:")
    client_code(ConcreteFactory1())

    print("\n")

    print("Client: Testing the same client code with the second factory type:")
    client_code(ConcreteFactory2())

Output.txt: 执行结果

Client: Testing client code with the first factory type:
The result of the product B1.
The result of the B1 collaborating with the (The result of the product A1.)

Client: Testing the same client code with the second factory type:
The result of the product B2.
The result of the B2 collaborating with the (The result of the product A2.)

抽象工厂在其他编程语言中的实现

抽象工厂在 C# 中的实现 抽象工厂在 Java 中的实现 抽象工厂在 PHP 中的实现 抽象工厂在 Ruby 中的实现 抽象工厂在 Swift 中的实现 抽象工厂在 TypeScript 中的实现