Sam,
Thanks for the rapid response. I think I see what you mean, but I'm
not sure it solves my problem.
Looking at the example you sent, here's how my problem would look in
that context:
- Friendship has an extra column called "degree_of_friendship", which
can be "meh", "good", or "great"
- I want to find all of Bob's "great" friends.
I can get Bob's great friendSHIPS by doing this:
Friendship.objects.filter(first = bob, degree_of_friendship = "great")
or I could get all of Bob's friends:
bob.friends.all()
but how do I get the Friend objects that are "great", but not others?
In other words, how do I impose a constraint on the Friendship join-
table when I do bob.friends?
-Ben
On Jun 1, 7:59 pm, Sam Chuparkoff <s...@sadach.org> wrote:
> On Mon, 2009-06-01 at 16:01 -0700, Ben Adida wrote:
> > I have a ManyToMany self relationship with a custom join table (I
> > don't think the self-reference is important to the problem, but it
> > might be, so I'm mentioning it):
>
> > class Documents
> > related_docs = models.ManyToManyField("self",
> > through='DocumentRels')
>
> > DocumentRels is a table that maps one document to another, with a
> > relationship type.
>
> > If I want all documents related to doc_0, I can just do:
>
> > doc_0.related_docs
>
> > But what if I want all documents related to doc_0 where I specify an
> > extra constraint on the join table, e.g. a value for
> > DocumentRels.relationship? Is there a way to do that without custom
> > SQL?
>
> You will not need custom sql, because DocumentRels is going to be a
> Model. When you want to filter based on DocumentRels.relationship, you
> will either use:
>
> DocumentRels.objects.filter()
>
> or go through the RelatedManagers that are added to your Document
> model for the ForeignKeys in DocumentRels. The reference is here:
>
> http://docs.djangoproject.com/en/dev/topics/db/models/#extra-fields-o...
>
> For code that exactly fits your case, see PersonSelfRefM2M in:
>
> http://code.djangoproject.com/browser/django/trunk/tests/modeltests/m...
>
> sdc
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