#31981: many_to_many add() does not trigger post_save signal for the through
class
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Reporter: Kurt Wheeler | Owner: nobody
Type: Uncategorized | Status: new
Component: Uncategorized | Version: 3.1
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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I have a many-to-many relationship on my organization model:
https://github.com/AlexsLemonade/resources-
portal/blob/dev/api/resources_portal/models/organization.py#L50. As you
can see, I specify `through="OrganizationUserAssociation"`, and that class
is defined here: https://github.com/AlexsLemonade/resources-
portal/blob/dev/api/resources_portal/models/associations/organization_user_association.py
In a branch I am working on, I am adding a post-save signal to
OrganizationUserAssociation. What I have found is that this isn't called
when `organization.members.add(user)` is called.
I can't actually tell if this is a bug or just poorly documented. The only
documentation I can find for the add() method is here:
https://docs.djangoproject.com/en/3.1/topics/db/examples/many_to_many/ and
it only shows the method being used for a single object. I think the
post_save signal isn't being triggered because add() is doing a bulk
update instead of creating the through class and saving that? Does add()
handle multiple objects, is that why bulk update is being used? I can't
actually find any documentation that indicates either way.
However, it makes sense to me that if add() is called with a single
object, and there is a `through` class for the many-to-many field, then
the `through` class should be used to create the relationship.
It seems like now I have to go through my code and find everywhere I
called add() and do it the less convenient way. (The unfortunate thing is,
that add() isn't that much more convenient than creating the association,
so I wish I had just been warned so I could avoid it altogether.)
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Ticket URL: <https://code.djangoproject.com/ticket/31981>
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