Are you sure? I just tested it (using the definitions from the
"Simplifying Association Objects" section) with the following at the
bottom:
if __name__ == '__main__':
user = User('log')
user.keywords = [Keyword('one'), Keyword('two')]
for uk in user.user_keywords:
print uk, uk.user
And the output was:
<__main__.UserKeyword object at 0x11235910> <__main__.User object at 0x11227f50>
<__main__.UserKeyword object at 0x11235a90> <__main__.User object at 0x11227f50>
ie. the UserKeyword objects were associated with the user.
Simon
On Thu, Mar 5, 2015 at 2:30 PM, Pavel S <pa...@schon.cz> wrote:
> Yes.
> However doing so:
>
> user.keywords = [ Keyword('one'), Keyword('two') ]
>
> ...will create UserKeywords with user unset. This is the problem.
>
>
> Dne čtvrtek 5. března 2015 15:11:20 UTC+1 Simon King napsal(a):
>>
>> I haven't looked at your code closely so I'm not sure what the problem
>> is, but I'm not sure your creator factory should be necessary. The
>> association proxy docs say that something like:
>>
>> kw = Keyword('one')
>> user.keywords.append(kw)
>>
>> has the same effect as:
>>
>> kw = Keyword('one')
>> uk = UserKeyword(kw)
>> user.user_keywords.append(uk)
>>
>> In this code, the UserKeyword's "user" property is not set explicitly,
>> but because of the backref on User.user_keywords, appending to the
>> list will cause the "user" property to be assigned.
>>
>> Simon
>>
>>
>> On Thu, Mar 5, 2015 at 11:46 AM, Pavel S <pa...@schon.cz> wrote:
>> > Hi,
>> >
>> > I just noticed that User.groups relationship is not needed at all (it
>> > was a
>> > relict of previous setup before System column was added).
>> > So the problem is completely gone.
>> >
>> > ---
>> >
>> > I already use AssociationProxy pattern in order to have relations like
>> > User.A_groups, User.B_groups, USer.C_groups.
>> > However I figured out other issue that 'creator' callback to
>> > AssociationProxy does not pass the parent object to it, which is weird.
>> > See example:
>> >
>> > user = ScopedSession.query(User).get('fred')
>> > user.A_groups = [ Group('admins') ]
>> >
>> > It should create also intermediary instance of User2Group. It does, but
>> > user
>> > attribute of intermediary object is null.
>> > So I created AssociationFactory as the following:
>> >
>> > class AssociationFactory(AssociationProxy):
>> > def __init__(self, *args, **kwargs):
>> > self.creator_factory = kwargs.pop('creator_factory')
>> >
>> > super(AssociationFactory, self).__init__(*args, **kwargs)
>> >
>> >
>> > def __get__(self, obj, class_):
>> > if obj:
>> > self.creator = self.creator_factory(weakref.ref(obj))
>> >
>> > return super(AssociationFactory, self).__get__(obj, class_)
>> >
>> >
>> > for system in ('A', 'B', 'C'):
>> > def creator_factory(user_ref):
>> > def creator(group):
>> > user = user_ref()
>> > if user is None:
>> > raise TypeError('Stale object reference')
>> > return User2Group(user=user, group=group, system=system)
>> > return creator
>> >
>> > setattr(User, system + '_groups',
>> > AssociationFactory(system+'_users2groups', 'group',
>> > creator_factory=creator_factory)
>> >
>> > Then all works nicely. Do you see the point?
>> > cheers!
>> >
>> >
>> > Dne čtvrtek 5. března 2015 11:58:50 UTC+1 Simon King napsal(a):
>> >>
>> >> Glad you've figured it out. This is touched on briefly in the docs, in
>> >> the note at the bottom of:
>> >>
>> >>
>> >>
>> >> http://docs.sqlalchemy.org/en/rel_0_9/orm/basic_relationships.html#association-object
>> >>
>> >> As an alternative to making User.groups a relationship, you could also
>> >> consider using the Association Proxy extension:
>> >>
>> >>
>> >>
>> >> http://docs.sqlalchemy.org/en/rel_0_9/orm/extensions/associationproxy.html#simplifying-association-objects
>> >>
>> >> Hope that helps,
>> >>
>> >> Simon
>> >>
>> >>
>> >> On Thu, Mar 5, 2015 at 10:43 AM, Pavel S <pa...@schon.cz> wrote:
>> >> > Hi,
>> >> > Adding viewonly=True on User.groups relationship solved the issue.
>> >> > cheers!
>> >> >
>> >> > Dne čtvrtek 5. března 2015 11:26:58 UTC+1 Pavel S napsal(a):
>> >> >>
>> >> >> Hello,
>> >> >>
>> >> >> I have relation User-User2Group-Group with additional attribute
>> >> >> System
>> >> >> on
>> >> >> User2Group table.
>> >> >> The System is part of primary key, which means 'user can me member
>> >> >> of
>> >> >> group via multiple systems'.
>> >> >>
>> >> >> class User(Base):
>> >> >> __tablename__ = 'User'
>> >> >>
>> >> >> name = Column('Name', Unicode(256), primary_key=True)
>> >> >>
>> >> >> class Group(Base):
>> >> >> __tablename__ = 'Group'
>> >> >>
>> >> >> name = Column('Name', Unicode(256), primary_key=True)
>> >> >>
>> >> >> class User2Group(Base):
>> >> >> __tablename__ = 'User2Group'
>> >> >>
>> >> >> userName = Column('UserName', Unicode(256),
>> >> >> ForeignKey(User.name),
>> >> >> primary_key=True)
>> >> >> groupName = Column('GroupName', Unicode(256),
>> >> >> ForeignKey(Group.name),
>> >> >> primary_key=True)
>> >> >> systemName = Column('SystemName', Enum('A', 'B', 'C'),
>> >> >> primary_key=True)
>> >> >>
>> >> >> User.groups = relationship(Group, secondary=User2Group.__table__)
>> >> >>
>> >> >>
>> >> >> Table User2Group looks like following
>> >> >>
>> >> >> UserName | GroupName | SystemName
>> >> >> ---------------------------------
>> >> >> fred | admins | A
>> >> >> fred | admins | B
>> >> >> fred | admins | C
>> >> >>
>> >> >>
>> >> >> However when trying to delete user 'fred' wich is assinged to group
>> >> >> 'admins' via multiple systems A, B, C.
>> >> >>
>> >> >> I'm getting error: DELETE statement on table 'User2Group' expected
>> >> >> to
>> >> >> delete 1 row(s); Only 3 were matched.
>> >> >>
>> >> >> Did I misconfigured something?
>> >> >>
>> >> >> Thanks
>> >> >>
>> >> > --
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