python - SQLAlchemy 未映射类错误 : Class 'sqlalchemy.ext.declarative.DeclarativeMeta' is not mapped

Question

我在我的项目中使用模型继承。

我的模型:

class CommentBase(Base):
    __abstract__ = True

    id = Column(Integer, primary_key=True)
    text = Column(Unicode(500))

    @declared_attr
    def user_id(cls):
        return Column(ForeignKey('user.id'))

    @declared_attr
    def user(cls):
        return relationship('User')

    def __init__(self, user_id, text):
        self.user_id = user_id
        self.text = text

class CommentOne(CommentBase):
    __tablename__ = 'comment_one'

class CommentTwo(CommentBase):
    __tablename__ = 'comment_two'

所有表都正确创建，但是当我尝试用一​​些测试数据填充表(即使是那些不从其他表继承的表)时，它会引发错误:

UnmappedClassError: Class 'sqlalchemy.ext.declarative.DeclarativeMeta' is not mapped

这是我的基础:

Base = declarative_base()

如果没有继承，一切都将按应有的方式工作。如何解决？

提前致谢!

Answer 1

我刚刚偶然发现了同样的问题。问题是我填充表格的方式:

s = application.models.Sample
s.label = 'asdf'
db_session.add(s)

UnmappedInstanceError: Class 'sqlalchemy.ext.declarative.api.DeclarativeMeta' is not mapped; was a class (application.models.Sample) supplied where an instance was required?

当我修复我的实例化时，它工作正常:

s = application.models.Sample()
...