#16073: Django admin save not sending post remove action with m2m changed signal
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Reporter: sam@… | Owner: nobody
Type: Bug | Status: new
Milestone: | Component: contrib.admin
Version: 1.3 | Severity: Normal
Keywords: m2m_changed | Triage Stage: Unreviewed
Has patch: 0 | Easy pickings: 0
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Hi all
I'm trying to get a many to many model to update when I save a related
model. This should be possible using the m2m_changed signal (and it works!
but not in the admin?) e.g.
{{{
# i want the references field to update when related model is saved.
# so just call count_references
class Tag(models.Model):
"""Group everything into categories"""
# stuff stuff stuff
references = models.IntegerField(default=0, editable=False)
def count_references(self):
# just add up references each time to save headaches
self.references = 0
# search for reverse managers
sets = re.compile('^\w+_set$')
for rel_set in [method for method in dir(self) if
sets.match(method)]:
self.references += getattr(self, rel_set).count()
self.save()
class Entry(models.Model):
"""Blog entry"""
# stuff stuff stuff
tags = models.ManyToManyField('Tag', blank=True)
# this will call count_references when entry adds or removes tags
@receiver(m2m_changed, sender=Entry.tags.through)
def update_tag_ref_count(sender, instance, action, reverse, model, pk_set,
**kwargs):
print action
if not reverse and action == 'post_add' or action == 'post_remove':
for tag_pk in pk_set:
print tag_pk
Tag.objects.get(pk=tag_pk).count_references()
print Tag.objects.get(pk=tag_pk).references
}}}
Everything works perfectly when run in the shell. e.g. with a tests.py
like so:
{{{
t = Tag.objects.all()[0]
s = Snippet.objects.all()[0]
s.tags.remove(t)
s.save()
s.tags.add(t)
s.save()
}}}
I get the following (where 'test' is the tag name being printed):
{{{
pre_remove
post_remove
test
0
pre_add
post_add
test
1
}}}
perfect! And when I add a tag to an entry in the admin I get the following
(between HTTP stuff):
{{{
pre_clear
post_clear
pre_add
post_add
test
1
}}}
still good! not sure what pre/post_clear was called for... and when I
remove:
{{{
pre_clear
post_clear
}}}
argh! pre/post_remove is not called! pre/post_clear is useless as well as
it doesn't provide any primary keys. this feels like a bug in the admin
implementation. any suggestions?
--
Ticket URL: <https://code.djangoproject.com/ticket/16073>
Django <https://code.djangoproject.com/>
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