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 <javascript:>>
> 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
> >> >>
> >> > --
> >> > You received this message because you are subscribed to the Google
> >> > Groups
> >> > "sqlalchemy" group.
> >> > To unsubscribe from this group and stop receiving emails from it,
> send
> >> > an
> >> > email to sqlalchemy+...@googlegroups.com.
> >> > To post to this group, send email to sqlal...@googlegroups.com.
> >> > Visit this group at http://groups.google.com/group/sqlalchemy.
> >> > For more options, visit https://groups.google.com/d/optout.
> >
> > --
> > You received this message because you are subscribed to the Google
> Groups
> > "sqlalchemy" group.
> > To unsubscribe from this group and stop receiving emails from it, send
> an
> > email to sqlalchemy+...@googlegroups.com <javascript:>.
> > To post to this group, send email to sqlal...@googlegroups.com
> <javascript:>.
> > Visit this group at http://groups.google.com/group/sqlalchemy.
> > For more options, visit https://groups.google.com/d/optout.
>
--
You received this message because you are subscribed to the Google Groups
"sqlalchemy" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to sqlalchemy+unsubscr...@googlegroups.com.
To post to this group, send email to sqlalchemy@googlegroups.com.
Visit this group at http://groups.google.com/group/sqlalchemy.
For more options, visit https://groups.google.com/d/optout.
