#25518: Multiple ManyToManyField related_name documentation
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Reporter: brandonchinn178 | Owner: nobody
Type: Uncategorized | Status: new
Component: Documentation | Version: 1.8
Severity: Normal | Keywords: manytomanyfield multiple
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
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I came across a bug [http://stackoverflow.com/questions/32957347/django-
manytomany-field-add-not-working the other day] about having a model with
multiple `ManyToManyFields` to the same `Model`. The bug occurs with the
following code:
{{{
# models.py
class MyModel(models.Model):
foo = models.ManyToManyField('other_app.OtherModel', related_name='+')
bar = models.ManyToManyField('other_app.OtherModel', related_name='+')
# shell
>>> x = MyModel.objects.create()
>>> y = OtherModel.objects.create()
>>> x.foo.add(y)
>>> x.foo.all() # returns []
}}}
So there's no errors or anything thrown. However, accessing with the
through model still works.
{{{
>>> x.foo.through.objects.all() # returns [<MyModel_othermodel object>]
}}}
I eventually found the answer in the
[https://docs.djangoproject.com/en/1.6/ref/models/fields/#django.db.models.ManyToManyField.related_name
Django documentation for version 1.6] saying that if you have more than
one `ManyToManyField` pointing to the same model, you need to set the
`related_name` to a '''''unique value''''' ending in `+`. However, this
description was removed starting in the 1.7 docs. I think we need to re-
add this in because it's a pretty significant specification about the
`ManyToManyField` I would never have found, if not for a
[http://stackoverflow.com/questions/13918968/multiple-many-to-many-
relations-to-the-same-model-in-django 2012 StackOverflow post].
--
Ticket URL: <https://code.djangoproject.com/ticket/25518>
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