Error Manager isn t accessible via model instances

Question

I'm trying to get model objects instance in another one and I raise this error :

 Manager isn't accessible via topic instance

Here's my model :

class forum(models.Model):
    # Some attributs

class topic(models.Model):
    # Some attributs

class post(models.Model):
    # Some attributs

    def delete(self):
        forum = self.topic.forum
        super(post, self).delete()
        forum.topic_count = topic.objects.filter(forum = forum).count()

Here's my view :

def test(request, post_id):
    post = topic.objects.get(id = int(topic_id))
    post.delete()

And I get :

post.delete()
forum.topic_count = topic.objects.filter(forum = forum).count()
Manager isn't accessible via topic instances

Answer 1

Hello @kartik,

The error caused when you try to access the Manager of a model through an instance of the model. You have used lower case class names. This makes it hard to say if the error is caused by an instance accessing the Manager or not. Since other scenarios that can cause this error are unknown I am proceeding on the assumption that you have somehow mixed up the topic variable so that you end up pointing to an instance of the topic model instead of the class.

This line has the error:

forum.topic_count = topic.objects.filter(forum = forum).count()
#                   ^^^^^

You have to use:

forum.topic_count = Topic.objects.filter(forum = forum).count()
#                   ^^^^^
#                   Model, not instance.

Hope it helps!!
Thank you!!