Hi,
I'm working on a project which makes extensive use of generic
relations. I'm having trouble with lookups across the generic
relation.
Cut-down version of the models:
class Post(models.Model):
text = models.TextField()
content_type = models.ForeignKey(ContentType)
object_id = models.PositiveIntegerField()
subject = generic.GenericForeignKey()
class Person(models.Model):
name = models.CharField(max_length=127)
site = models.ManyToManyField(Site)
....
posts = generic.GenericRelation(Post)
class Organisation(models.Model):
name = models.CharField(max_length=127)
site = models.ManyToManyField(Site)
....
posts = generic.GenericRelation(Post)
class Item(models.Model):
name = models.CharField(max_length=127)
site = models.ManyToManyField(Site)
....
posts = generic.GenericRelation(Post)
>From an individual Post, I can get the related item's name easily via
the subject attribute:
>>> p=Post.objects.get(pk=1)
>>> p.subject.name
u'Joe Bloggs'
But the problem comes when trying to do lookups from the Post model
via the generic relation, again using the subject attribute:
>>> Post.objects.filter(subject__name="Joe Bloggs")
<snip traceback>
TypeError: Cannot resolve keyword 'subject' into field. Choices are:
organisation, person, item, ... id, text, content_type, object_id
It seems that the "subject" attribute, despite being directly defined
in the Post model, is only available from instances - in lookups, you
can only use the individual models the Post is (generically) related
to.
Now I could change that filter to use the models explicitly -
Post.objects.filter(Q(person__name="Joe Bloggs") |
Q(organisation__name="Joe Bloggs"))
- but that seems to defy the purpose of generic relations, and would
mean having to remember to change the lookup if I added another model.
Am I doing something wrong, or is this a bug in generic relations? If
so, is it one of those that is going to be fixed Real Soon Now in
queryset-refactor?
Thanks for any ideas,
DR.
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