How to update value in the table referenced by foreign key in Django

Question

I have comment model that references (foreign key) a post model and there is a boolean field in the post model that tells whether this particular post has any comment or not.

• What I want to do is to update this boolean field of the post whenever a comment is made on that post, for this what do I have to do in the view.

• Also when I show all the posts on a page, I want to show those first which do not have any comment, so that people can comment on them.

How can I effectively do the following two things

Answer 1

You could use the comment_was_posted signal to update the associated Post once there is a new comment. See this thread to get the general idea: Django notification on comment submission

Although it might be better in this case to create a count_comments() method on your Post model.

To order and filter your Posts by the number of Comments for a given Post check Django's docs on aggregation or this blog post: http://agiliq.com/blog/2009/08/django-aggregation-tutorial/