On 05/11/2014 18:16, Carl Meyer wrote:
Hi,
On 11/05/2014 11:09 AM, Some Developer wrote:
I'm trying to write my own implementation of the Django comments
framework for various reasons and am wondering how one would link
comments to a particular object (model) of another type. For instance I
could have a ForeignKey in the Comment model pointing to a Blog post
article but that would mean that you could only leave comments on Blog
post articles. I want to be able to configure my Comment model so that
it can link to any other object of any type.
Does anyone know how to do that? I think it has something to do with the
ContentType framework that comes with Django but I have never used it
before so I'm not entirely sure.
I think this is what you're looking for:
https://docs.djangoproject.com/en/1.7/ref/contrib/contenttypes/#generic-relations
However, by using GenericForeignKey you give up some valuable things:
the database can no longer enforce referential integrity on those
relationships, and joins become more complex and often slower. So I
would recommend at least considering alternatives.
One possible alternative is to instead provide the bulk of your Comment
model as an abstract base model class, and then have users of your
comment app create their own Comment model inheriting from your abstract
base, and adding a single FK to whatever model they want comments on.
(This presumes that most users of your comments app will only need
comments on a single model in a given system; or if they want comments
on more than one model, they don't mind having two separate Comment
models to handle that.)
Carl
Thanks for the info. You make some interesting points about the database
not being able to enforce referential integrity.
I hadn't thought of providing the comment model as a base class and
having the users specialise it themselves. How would that work in
regards to template tags? For instance if I had a template tag like this:
{% get_comments for obj as var %}
how would one hook in a user provided object with its own model which is
not known ahead of time or would you suggest using a template tag such
as this instead? I guess letting the user explicitly state the
application and the model themselves offers the best flexibility in the
long run.
{% get_comments for [app].[model] [object_id] %}
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