Django GenericRelation not working

Question

I have the following model in my app, using the content-type django framework :

class GenericMedia(models.Model):
    limit           = models.Q(model = 'Image') | models.Q(model = 'Video') | models.Q(model = 'Other')
    content_type    = models.ForeignKey(ContentType, limit_choices_to = limit)
    object_id       = models.PositiveIntegerField()
    content_object  = generic.GenericForeignKey('content_type', 'object_id')

    def __unicode__(self):
        return u"%s" % os.path.basename(self.content_object.url.name)

    def instance(self):
        return self.content_object.__class__.__name__


class Media(models.Model):
    description     = models.CharField(blank = True, max_length = 500)
    link            = models.URLField(blank = True)
    genericFK       = generic.GenericRelation(GenericMedia, content_type_field='content_type', object_id_field='object_id')

    class Meta:
        abstract = True

    def __unicode__(self):
        return u"%s" % os.path.basename(self.url.name)

    def save(self, *args, **kwargs):
        super(Media, self).save(*args, **kwargs)
        generic_link = GenericMedia(content_object = self)
        generic_link.save()


class Image(Media):
    imgW = models.PositiveSmallIntegerField()
    imgH = models.PositiveSmallIntegerField()
    url  = models.ImageField(upload_to = 'mediamanager', height_field = 'imgH', width_field = 'imgW')

Everythings works fine, excepts the GenericRelation in my abstract Media Class. In django documentation it is said that :

If you delete an object that has a GenericRelation, any objects which have a GenericForeignKey pointing at it will be deleted as well.

But my problem is that when I delete an image, the GenericMedia pointing to it is not deleted.

If anyone has a solution, thanks !

Answer 1

As you mentioned it, the documentation is clear about what happens when you delete an object that has a Generic Relation field (Django deletes all objects that have a foreign key to the object with GenericRelation).

So this is basically Django's fault (probably some problem with the abstract classes), BUT there is a way to overcome this situation.

By using pre_delete you can delete all objects that have a foreign key to the object with GenericRelation.

Some examples of pre_delete signal can be found here: http://www.koopman.me/2015/01/django-signals-example/