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
The error in question is 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 is the culprit:
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.
What is going wrong? objects
is a Manager
available at the class level, not to the instances. See the documentation for retrieving objects for details. Money quote:
Managers
are accessible only via model classes, rather than from model instances, to enforce a separation between "table-level" operations and "record-level" operations.
(Emphasis added)
Update
See the comments from @Daniel below. It is a good idea (nay, you MUST :P) to use title case for class names. For instance Topic
instead of topic
. Your class names cause some confusion whether you are referring to an instance or a class. Since the Manager isn't accessible via <model> instances
is very specific I am able to offer a solution.The error may not be so self evident always.