[Answered ]-Django – query and delete GenericForeignKey

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That’s because there can in fact be duplicate ids in the GenericForeignKey. E.g. if you have a Photo model and an Article model, both with an Entry associated with it, the photo’s primary key can be the same value as the article’s primary key, and the object_ids will be the same. That’s why you need both a content_type and an object_id to begin with.

To get the right object, you need to check for both the type and id. 

from django.contrib.contenttypes.models import ContentType

def delete_entry(sender, instance, **kwargs):
    content_type = ContentType.objects.get_for_model(instance)
    entry = Entry.objects.get(content_type=content_type, 
                              object_id=instance.id)
    entry.delete()

Another way to accomplish this is to use a GenericRelation (see documentation). This is the reverse relation of a GenericForeignKey. Whenever an object with a GenericRelation is deleted, this cascades to any objects of the supplied model with a GenericForeignKey pointing to that instance:

from django.contrib.contenttypes.generic import GenericRelation

class Photo(models.Model):
    ...
    entries = GenericRelation(Entry, content_type_field='content_type', 
                              object_id_field='object_id')
👤knbk

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