Question

I have an app which essentially a conversation system (much like reddit).

Where a post can have multiple replies, and a reply and have multiplies, and a reply to a reply can have multiple replies (etc.)

I’ve made the model like this:

class Discussion(models.Model):
    message = models.TextField()
    replies = models.ManyToManyField('self')

and the view:

discussions = Discussions.objects.all()

and the template looks like this:

{% for discussion in discussions %}
    {{ discussion.message }}
{% endfor %}

How would I go about making a system where I can output all replies like this?

discussion
    reply
        reply
    reply
        reply
            reply
                reply

Which would go down as far as it needs to to ensure all replies are listed.

Answer 1

Unless a reply can be a reply to multiple posts, a ManyToManyField isn’t what you want. You just need a ForeignKey:

class Discussion(models.Model):
    message = models.TextField()
    reply_to = models.ForeignKey('self', related_name='replies', 
        null=True, blank=True)

Then you can get to a Discussion’s replies with Discussion.replies.

Unfortunately, there’s no way to do a recursion in Django’s template language, so you have to either 1) run a recursive function to get a “flattened” list of replies, and put that in the context, or 2) write a function that can be called recursively that uses a template to generate each level, which would look something like:

_DiscussionTemplate = Template("""
<li>{{ discussion.message }}{% if replies %}
    <ul>
        {% for reply in replies %}
        {{ reply }}
        {% endfor %}
    </ul>
{% endif %}</li>
""".strip())

class Discussion(models.Model):
    message = models.TextField()
    reply_to = models.ForeignKey('self', related_name='replies', 
        null=True, blank=True)

    @property
    def html(self):
        return _DiscussionTemplate.render(Context({
            'discussion': self,
            'replies': [reply.html() for reply in self.replies.all()]
        }))

Then in your top-level template, you just need:

<ul>
    {% for d in discussions %}
    {{ d.html }}
    {% endfor %}
</ul>

Apply CSS as desired to make it look nice.

EDIT: Root discussions are those in Discussion.objects.filter(reply_to=None). And all the code, _DiscussionTemplate included, goes in your models.py. This way, _DiscussionTemplate is initialized once when the module loads.

EDIT 2: Putting the HTML in a template file is pretty straightforward. Change the view code that sets _DiscussionTemplate to:

_DiscussionTemplate = loader.get_template("discussiontemplate.html")

Then create discussiontemplate.html:

<li>{{ discussion.message }}{% if replies %}
    <ul>
        {% for reply in replies %}
        {{ reply }}
        {% endfor %}
    </ul>
{% endif %}</li>

Set the path to the template file as needed.