CODEWITHSUNDEEP
pythondjangotree
Enrico Tuvera Jr
Enrico Tuvera Jr

Reputation: 2817

Django - Using trees to build a comment system

A few days back I was messing around with Django, trying to get a feel for how stuff works, when I decided to try and build a simple forum, one that resembled a forum that I frequented (but is now closed down). The idea was that each of the comments would be parent to any number of comments, like so:

 comment <--top
   comment <-- comment "A"
   comment <-- comment "B"
   comment <-- comment "C"
     comment <--C-1, reply to comment "C"
       comment <-- C-1-1, reply to comment "C-1"
         comment 
           comment 
             comment
         comment <-- C-1-1-1 reply to C-1-1
         comment 
         comment
           comment
             comment
     comment
     comment
       comment
         comment
           comment
             comment
             comment
             comment

The idea here is that replies to a comment would stuffed one level beneath it, and each comment, with the exception of the very first comment, has a parent. The thing is, although I get the idea behind implementing tree traversals, none of the books/articles I've read on the subject take Django into account (or the MVC pattern for that matter), so my question is how would I go about implementing this system in Django? (here's the model code i've got for reference :-/)

class Comment(models.Model): 
 Parent = models.OneToOneField('self', null=True)
 Children = models.ForeignKey('self', null=True)

 Author = models.ForeignKey(User)
        Author_IP = models.IPAddressField()
 Created_On = models.DateTimeField(auto_now_add=True)
 Modified_On = models.DateTimeField(auto_now=True)
 Body = models.TextField()

Upvotes: 0

Views: 1845

Answers (2)

Benjamin Wohlwend
Benjamin Wohlwend

Reputation: 31828

Have a look at django-threadedcomments. It's purpose is more fit to be used as comments on a blog than a full featured forum, but if it doesn't fit your case, you can at least look at the source code and learn a couple things from it.

As far as tree-based structures go, there are three projects I'm aware of for Django's ORM: django-mptt (this one has the biggest "market share" with 3rd party django apps AFAIK), django-treebeard, and easytree (which is based on treebeard). Easytree comes with a nice admin interface, but the other two projects have at least patches in their issue trackers to add an admin interface (not sure if they integrated those patches already).

Upvotes: 2

czarchaic
czarchaic

Reputation: 6318

I would only define the parent and give it a related name

class Comment(models.Model):
  parent=models.ForeignKey('self', related_name="children", null=True, blank=True)
  #other fields

Then you could get its children

comment=Comment.objects.get(id=1)
children=comment.children.all()

for child in children:
  morechildren=child.children.all()

Upvotes: 1

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