Widget to display categories as tree in Django admin

Question

is there any existing code to display the list of some Category object in the admin of a Django site? Ideally I'd like some tree representation like

cat_1

----cat_1_1

----cat_1_2

cat_2

cat_3

----cat_3_1

----cat_3_2

----cat_3_3

with up/down button to change the order.

class Category(models.Model):

    parent = models.ForeignKey('self', null=True, related_name='children')
    name = models.CharField(max_length=100)

Answer 1

Firstly, you haven't actually defined an order on this model - just a parent. You need something like MPTT which keeps track of the level and the position within that level.

Given that, it's fairly easy to write a __unicode__ method for the model which displays the number of hyphens equal to the category's level:

def __unicode__(self):
   return '%s%s' % ('-' * self.level, self.name)

As for the up/down button, you'll need to write that in Javascript, I expect.

Answer 2

Here is one widget, based on django-mptt :
http://anentropic.wordpress.com/2009/11/05/more-django-mptt-goodness-filteredselectmultiple-m2m-widget/

looks like what you're looking for