python SQLModel中的SQLModel混合(基类)

Question

我正在使用SQLModel，并且希望用created_at字段定义基类，以便在其他模型中继承它。

class CreatedAtMixin(SQLModel):
    created_at: datetime = Field(default=datetime.now(timezone.utc), nullable=False)

但是当我试图在其他模型中使用它时，像这样通过alembic进行迁移

class NetworkBase(SQLModel, CreatedAtMixin):
    name: str = Field(max_length=64, description='Name of network')
    short_name: str = Field(max_length=32, description='Short name of the network')

我面临一个问题：

Traceback (most recent call last):
  File "/Users/nikitasamaev/PycharmProjects/new-checkout-backend/venv/bin/alembic", line 8, in <module>
    sys.exit(main())
  File "/Users/nikitasamaev/PycharmProjects/new-checkout-backend/venv/lib/python3.9/site-packages/alembic/config.py", line 588, in main
    CommandLine(prog=prog).main(argv=argv)
  File "/Users/nikitasamaev/PycharmProjects/new-checkout-backend/venv/lib/python3.9/site-packages/alembic/config.py", line 582, in main
    self.run_cmd(cfg, options)
  File "/Users/nikitasamaev/PycharmProjects/new-checkout-backend/venv/lib/python3.9/site-packages/alembic/config.py", line 559, in run_cmd
    fn(
  File "/Users/nikitasamaev/PycharmProjects/new-checkout-backend/venv/lib/python3.9/site-packages/alembic/command.py", line 227, in revision
    script_directory.run_env()
  File "/Users/nikitasamaev/PycharmProjects/new-checkout-backend/venv/lib/python3.9/site-packages/alembic/script/base.py", line 563, in run_env
    util.load_python_file(self.dir, "env.py")
  File "/Users/nikitasamaev/PycharmProjects/new-checkout-backend/venv/lib/python3.9/site-packages/alembic/util/pyfiles.py", line 92, in load_python_file
    module = load_module_py(module_id, path)
  File "/Users/nikitasamaev/PycharmProjects/new-checkout-backend/venv/lib/python3.9/site-packages/alembic/util/pyfiles.py", line 108, in load_module_py
    spec.loader.exec_module(module)  # type: ignore
  File "<frozen importlib._bootstrap_external>", line 850, in exec_module
  File "<frozen importlib._bootstrap>", line 228, in _call_with_frames_removed
  File "app/db/migrations/env.py", line 12, in <module>
    from app.models import *
  File "/Users/nikitasamaev/PycharmProjects/new-checkout-backend/app/models/__init__.py", line 1, in <module>
    from app.models.blockchain import Network
  File "/Users/nikitasamaev/PycharmProjects/new-checkout-backend/app/models/blockchain.py", line 9, in <module>
    class NetworkBase(SQLModel, CreatedAtMixin):
  File "/Users/nikitasamaev/PycharmProjects/new-checkout-backend/venv/lib/python3.9/site-packages/sqlmodel/main.py", line 277, in __new__
    new_cls = super().__new__(cls, name, bases, dict_used, **config_kwargs)
  File "pydantic/main.py", line 149, in pydantic.main.ModelMetaclass.__new__
  File "pydantic/config.py", line 118, in pydantic.config.inherit_config
TypeError: Cannot create a consistent method resolution
order (MRO) for bases Config, Config

当然，我可以在我的NetworkBase和其他模型中手动设置字段NetworkBase，它可以在没有任何问题的情况下工作，但是我想继承CreatedAtMixin。

解决这个问题的方法是什么？

Answer 1

您需要取出SQLModel继承，因为它已经是第一个类中的SQLModel类：

class CreatedAtMixin(SQLModel):
    created_at: datetime = Field(default=datetime.now(timezone.utc), nullable=False)

class NetworkBase(CreatedAtMixin):
    name: str = Field(max_length=64, description='Name of network')
    short_name: str = Field(max_length=32, description='Short name of the network')