Hi,
I'm still having troubles correctly figuring my various many-to-many
relations. Originally, this was a 'standard' many-to-many; that is, a
secondary table was specified.
However, I now need to add further information to the relation and am
converting into an AssociationObject. My problem is in ensuring that the
original calls still work. So, currently I have:
class Association(Base):
__tablename__ = 'objecta_objectb'
objecta_id = Column(Integer, ForeignKey('objecta.id'), primary_key=True)
objectb_id = Column(Integer, ForeignKey('objectb.id'), primary_key=True)
objecta = relationship("ObjectA", backref = "associations", cascade =
'all, delete-orphan')
objectb = relationship("ObjectB", backref = "associations", cascade =
'all, delete-orphan')
def __init__(self, objecta = None, objectb = None):
self.objecta = objecta
self.objectb = objectb
pass
class ObjectA(Base):
objectbs = association_proxy('associations', 'objectb', creator=lambda
b:
Association(objectb=b))
class ObjectB(Base):
objectas = association_proxy('associations', 'objecta', creator=lambda
a:
Association(objecta=a))
The point of all this is so that I can create the associations by doing:
objecta_instance.objectbs.append(objectb_instance)
or
association_instance = Association(objectb = objectb_instance)
objecta_instance.associations.append(association_instance)
Sorry if the above is rather convoluted; it is based on
http://www.preetk.com/node/sqlalchemy-part-2-declarative-bi-directional-association-classes/,
which is somewhat clearer.
Anyway, using the above I get:
AssertionError: Dependency rule tried to blank-out primary key column
'objecta_objectb.objectb_id' on instance '<Association at 0x109277b90>'
What am I doing wrong? I understand that it is somehow related to how the
cascade is set up, but I'm not sure how to move forward.
Thanks,
Ben
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