How to correctly fill in Django ManyToMany field in post_save trigger?

Question

Django

Hello, I'm trying to populate a ManyToMany field in a post_save trigger. Approximate code looks like this:

@receiver(post_save, sender=Post, dispatch_uid='update_post_images')<br>
def update_post_images(sender, instance, using, **kwargs):<br>
   post_save.disconnect(update_post_images, sender=Post, dispatch_uid='update_post_images')<br>
   print 'before', instance.images.all()<br>
   img = Image.object.get(pk=1469)<br>
   instance.images.add(img)<br>
   print 'after', instance.images.all()<br>
   post_save.connect(update_post_images, sender=Post, dispatch_uid='update_post_images')<br>

Now I see everything in the server console as it should be.
print 'before', instance.images.all() - displays one image
print 'after', instance.images.all() - displays 2 (the old one and the one that was added) But after the trigger has worked ,
nothing changes because
e. in manage.py shell at the request Post.objects.get(pk=.....).images.all() - I still see the same ONE object (and in the admin panel too)
Please help me solve the problem.

Answer 1

here is the code that helped (found here: stackoverflow.com/questions/4432385/django-how-to-...

class MyModel(models.Model):

    m2mfield = ManyToManyField(OtherModel)

    @staticmethod
    def met(sender, instance, action, reverse, model, pk_set, **kwargs):
        if action == 'pre_add':
            # here you can modify things, for instance
            pk_set.intersection_update([1,2,3]) 
            # only save relations to objects 1, 2 and 3, ignoring the others
        elif action == 'post_add':
            print pk_set
            # should contain at most 1, 2 and 3

m2m_changed.connect(receiver=MyModel.met, sender=MyModel.m2mfield.through)