在 sqlalchemy 中实现 django User.objects.get_by_id 风格

[wuwukai007]

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import DeclarativeMeta

class BaseController:
    """
    Base BaseController, implement base CRUD sqlalchemy operations
    """

    model_cls = None
    base_filter = ()
    
    def get_by_id(
        cls,
        model_id: Union[int, str],
        query_field: Union[List, tuple] = None,
        to_dict: bool = False,
        id_field: str = None,
    ) -> Model or None:
        session.query(cls.model_cls).filter


class CustomDeclarativeMeta(DeclarativeMeta):

    def __init__(self, *args, **kwargs):
        super(CustomDeclarativeMeta, self).__init__(*args, **kwargs)
        if hasattr(self, 'objects'):
            self.objects.model_cls = self
            self.objects.base_filter = (self.objects.model_cls.is_delete == 0,)


Base = declarative_base(metaclass=CustomDeclarativeMeta)

class BaseModel(Base):
    """基类表模板"""

    __abstract__ = True
    objects = BaseController()
    is_delete = Column(Boolean, nullable=False, default=False, comment="是否已删除")


class User(BaseModel):
    nickname = Column("nickname", String(255), index=True, comment="昵称")


User.objects.get_by_id(1)

[XueXianqi]

`get_by_id` 既然是个类方法，就需要加装饰器 `@classmethod`，而且出参的类型提示 `Model or None` 也不对，可能是 Model 或者 None 应该用 Optional[Model]，况且这个方法里面也没有 return 任何内容，返回一定是 None ，逻辑有点问题...

[wuwukai007]

就是为了不用类方法才用的元类，另外这个方法 pass ，只是提供了一个入口，自己实现