Martijn Faassen wrote:
>
> Hey,
>
> Michael Bayer wrote:
>> subclass RelationProperty fine, but don't get involved with overriding
>> its
>> internal _xxx methods.
>
> So:
>
> Override do_init() completely (not calling the super do_init()).
no, call do_init().
def do_init(self):
self.primaryjoin = figure_out_my_primary_join()
super(RelationProperty, self).do_init()
>
> Problem: the backref will already have been set up, and this will not
> get the custom arguments.
the backref you can roll without using backref(). set up your custom
relation() on the other side and then establish the two-way communication
using the "back_populates" argument on both relations.
http://www.sqlalchemy.org/trac/browser/sqlalchemy/trunk/test/orm/test_relationships.py#L803
is an example.
>
> It's pretty involved, ugly, and fragile. It'd be nicer if there was a
> way to do this generically, as I just want to add a custom condition to
> the automatically set up primary...
I *really* try to avoid adding new arguments and flags as quick solutions
to single-user use cases, unless there is truly no other way to accomplish
the desired goal. the "back_populates" argument is an example of opening
up the mechanics of "backref" in a more generalized way.
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