如何在Python中使用可调用而不是抽象工厂模式？

Question

我一直在尝试弄清楚在Python中何时何地使用不同的模式。我偶然发现了这个文档：https://python-patterns.guide/gang-of-four/abstract-factory/

现在，这让我想知道，我如何才能按照他在我的代码中所说的做。这是我的实现是一个抽象工厂。不确定是否正确。

from abc import abstractmethod, ABC

from sqlalchemy.orm import Session

from managers.database_manager import DatabaseManager
from managers.log_manager import LogManager
from managers.sqlalchemy_manager import get_db
from models.bal.post import Post
from models.dal.models import Post as ORMPost


class PostsManager(ABC):
    def __init__(self):
        pass

    @abstractmethod
    def get_posts(self):
        pass

    @abstractmethod
    def get_post(self, post_id):
        pass

    @abstractmethod
    def create_post(self, post: Post):
        pass

    @abstractmethod
    def delete_post(self, post_id):
        pass

    @abstractmethod
    def update_post(self, post_id, post: Post):
        pass


class PostsManagerFactory:
    @staticmethod
    def get_posts_manager(use_orm=True) -> PostsManager:
        if use_orm:
            return PostsManagerWithORM()
        else:
            return PostsManagerWithoutORM()


class PostsManagerWithORM(PostsManager):

    def get_posts(self):
        db: Session = get_db()
        posts = db.query(ORMPost).all()
        return posts

    def get_post(self, post_id):
        pass

    def create_post(self, post: Post):
        pass

    def delete_post(self, post_id):
        pass

    def update_post(self, post_id, post: Post):
        pass


class PostsManagerWithoutORM(PostsManager):
    def __init__(self):
        super().__init__()
        self.db_manager = DatabaseManager()

    def get_posts(self):
        posts = self.db_manager.execute_query("select * from posts")
        return posts

    def get_post(self, post_id):
        post = self.db_manager.execute_query("SELECT * FROM posts WHERE id='%s'", (post_id,), single_record_flag=True)
        return post

    def create_post(self, post: Post):
        post = self.db_manager.execute_query("INSERT INTO posts (title, content) VALUES (%s, %s) RETURNING *",
                                             (post.title, post.content), single_record_flag=True)

        return post

    def delete_post(self, post_id):
        post = self.db_manager.execute_query("DELETE FROM posts WHERE id = %s RETURNING *", (post_id,),
                                             single_record_flag=True)
        return post

    def update_post(self, post_id, post: Post):
        post = self.db_manager.execute_query(
            "UPDATE posts SET title = %s, content = %s, published = %s WHERE id= %s RETURNING *",
            (post.title, post.content, post.published, post_id),
            single_record_flag=True)
        return post

下面是我调用这些方法的方式：

posts_manager = PostsManagerFactory.get_posts_manager()
posts = posts_manager.get_posts()

我的第一个问题，这是使用抽象工厂模式的正确方式吗？如果没有，请让我知道，我可能会问一个新的问题。不管怎么说，如果是这样的话，为什么文档说使用可伸缩模式比使用抽象工厂模式更好，在这种情况下我该怎么做呢？

Answer 1

在你的最后一条评论之后。

对于这个用例，我不会使用抽象工厂模式。我可以问一下你为什么要用它吗？

当我建议通过提取函数的get_posts_manager来删除PostsManagerFactory类时，我指的是替换以下代码片段

class PostsManagerFactory:
    @staticmethod
    def get_posts_manager(use_orm=True) -> PostsManager:
        if use_orm:
            return PostsManagerWithORM()
        else:
            return PostsManagerWithoutORM()

有了这个

def get_posts_manager(use_orm=True) -> PostsManager:
    if use_orm:
        return PostsManagerWithORM()
    else:
        return PostsManagerWithoutORM()

你可能想要这样缩短

def get_posts_manager(use_orm=True) -> PostsManager:
    return PostsManagerWithORM() if use_orm else PostsManagerWithoutORM()

然后，您只需通过调用函数即可在代码中使用它

posts_manager = get_posts_manager() # <----
posts = posts_manager.get_posts()