在单独的文件 FLASK、SQLalchemy 中创建模型之间的关系

Question

当这两个模型当前位于不同的文件夹中时，如何在它们之间正确建立外键关系？

from sqlalchemy import Column, String, Integer, DateTime, ForeignKey
from testserver.database import Base
from datetime import datetime


class Service(Base):
    __tablename__ = 'services'

    id = Column(Integer(), primary_key=True)
    name = Column(String(25), nullable=False, unique=True)
    description = Column(String(80), nullable=False)
    date_created = Column(DateTime(), default=datetime.utcnow)
    provider_id = Column(String, ForeignKey('provider.id'))

from sqlalchemy import Column, String, Integer, DateTime
from sqlalchemy.orm import relationship
from testserver.database import Base
from datetime import datetime
from testserver.database import db_session


class Provider(Base):
    __tablename__ = 'providers'

    id = Column(Integer(), primary_key=True)
    name = Column(String(25), nullable=False, unique=True)
    description = Column(String(80), nullable=False)
    date_created = Column(DateTime(), default=datetime.utcnow)
    services = relationship(
        'Service', cascade='all, delete-orphan', backref='provided_by')

from sqlalchemy.ext.declarative import declared_attr


class Base(object):
    __abstract__ = True

    @declared_attr
    def __tablename__(cls):
        return cls.__name__.lower()

上面的代码目前抛出一个错误：

sqlalchemy.exc.NoReferencedTableError: Foreign key associated with column 'services.provider_id' could not find table 'provider' with which to generate a foreign key to target column 'id'

如有任何建议或解决方案，我们将不胜感激

Answer 1

我假设你这里有错字：

provider_id = Column(String, ForeignKey('provider.id'))

在关系中，您提供了小写的模型名称，而不是 table 名称。如果您将 provider 替换为 providers（因为它是您的 table 的名称）它应该可以解决您的问题

provider_id = Column(String, ForeignKey('providers.id'))

在单独的文件 FLASK、SQLalchemy 中创建模型之间的关系

Creating relationship between models when in separate files FLASK, SQLalchemy

python

sqlalchemy

flask