"secondary" requires a Table object as its argument. it is not
recommended to create a relation that uses a mapped table as its
"secondary" unless the relation specifies viewonly=True.
Jae Kwon wrote:
>
> Is there a way to declaratively create many to many relationships
> where the 'secondary' parameter for the relationship is deferred ?
>
> I couldn't get this to work, e.g.
>
> class User(DeclarativeBase):
> id = Column(Integer, primary_key=True)
> name = Column(String(20))
> groups = relation("Group", primaryjoin=("User.id ==
> GroupMember.user_id"), secondaryjoin=("GroupMember.group_id ==
> Group.id"), secondary="GroupMember")
>
> (the other classes are defined later).
>
> I was able to get around this with the following patch.
>
> --- a/sqlalchemy0.5/lib/sqlalchemy/orm/properties.py Mon Aug 31
> 22:37:21 2009 -0700
> +++ b/sqlalchemy0.5/lib/sqlalchemy/orm/properties.py Tue Sep 01
> 22:11:07 2009 -0700
> @@ -736,7 +745,11 @@
> # accept callables for other attributes which may require
> deferred initialization
> for attr in ('order_by', 'primaryjoin', 'secondaryjoin',
> 'secondary', '_foreign_keys', 'remote_side'):
> if util.callable(getattr(self, attr)):
> - setattr(self, attr, getattr(self, attr)())
> + called_value = getattr(self, attr)()
> + # the 'secondary' param requires a table, not a
> declarative class...
> + if attr == 'secondary' and hasattr(called_value,
> '__mapper__'):
> + called_value = called_value.__mapper__.mapped_table
> + setattr(self, attr, called_value)
>
> # in the case that InstrumentedAttributes were used to
> construct
> # primaryjoin or secondaryjoin, remove the "_orm_adapt"
> annotation so these
>
> - Jae
>
> >
>
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