this works (been working on getting this kind of thing into recipes/docs/books)
from sqlalchemy import Column, Integer, ForeignKey, String
from sqlalchemy.ext.declarative import declarative_base, declared_attr
from sqlalchemy.orm import relationship
Base = declarative_base()
class Mixin(object):
@declared_attr
def foob(cls):
cls.Blah = Blah = type("%sBlah" % cls.__name__,
(Base, ),
dict(
__tablename__ = 'blah_%s' % cls.__tablename__,
id = Column(Integer, primary_key=True),
name_id = Column(Integer, ForeignKey(cls.id))
)
)
return relationship(Blah)
class Name(Mixin, Base):
__tablename__ = "name"
id = Column(Integer, primary_key=True)
name = Column(String)
class Name2(Mixin, Base):
__tablename__ = "name2"
id = Column(Integer, primary_key=True)
name = Column(String)
print Name2.foob.contains(Name2.Blah())
On Apr 25, 2011, at 9:28 PM, Andrey Petrov wrote:
> Looks like this almost-sorta works:
>
> class TagMixin(object):
> @declared_attr
> def TagClass(cls):
> class Tag(BaseModel):
> __tablename__ = "tag_%s" % cls.__tablename__
>
> id = Column(types.Integer, primary_key=True)
> time_created = Column(types.DateTime, default=datetime.now,
> nullable=False)
>
> row_id = Column(types.Integer, ForeignKey(cls.id), index=True)
> name = Column(types.String, nullable=False, index=True)
>
> # This part breaks with... sqlalchemy.exc.InvalidRequestError: Table
> 'tag_user' is already defined for this MetaData instance.
> # @declared_attr
> # def tags(cls):
> # return orm.relationship(cls.TagClass, backref='tagged')
>
> class User(BaseModel, TagMixin):
> __tablename__ = 'user'
>
> id = Column(types.Integer, primary_key=True)
> ...
>
> The appropriate tables do get generated on create_all(). But as soon as I
> touch the User.TagClass attribute, it barfs with the same error again:
>
> InvalidRequestError: Table 'tag_user' is already defined for this MetaData
> instance. Specify 'extend_existing=True' to redefine options and columns on
> an existing Table object.
>
>
>
>
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