This is a follow up to the previous post on managing and visualizing trees using django. I’ve been using MPTT quite a bit now and it’s great – also, I looked deeper into the admin integration (basically, the issue of being able of manage trees from within the admin).

The major issue I had with the patch discussed in my previous post was the fact that it is mainly a javascript hack – everything is done in the browser – i.e. it looked wonderful but it didn’t really scale up. So if you had a lot of items in your tree (say thousands) the js-driven pagination (basically, hiding and showing things on demand) would crash – at least, it did that to me all the time!

The solution has been to reuse the admin management section from the FeinCMS project – this is a great CMS created by a bunch of django-ers in Switzerland – it relies heavvily on django’s admin so they had the same problem when having to provide a way for users to add structure to the pages in a website. With some help from google and Matthias (tx! he’s one of the guys behind FeinCMS) I got it all working.. here’s the main steps:

1. upgrade to django 1.1
This might not be necessary, cause everything is supposed to work also with the previous release – I tried it with django 1.0 too but I had to fix a couple of urls to make it work (Basically media files which were not loaded properly). So, if you want a hassle-free installation just upgrade to django 1.1 ! (which is great btw)

2. download and add feincms, mptt to you installed apps in settings.py
As simple as that.

INSTALLED_APPS = (
    ....
    'mptt',
    'feincms',
)

3. specify a url-path for feincms media in settings.py, and also a location (this may vary in your live server, if you want apache to serve these files directly).

FEINCMS_ADMIN_MEDIA = '/feincms_media/'
FEINCMS_ADMIN_MEDIA_LOCATION = '/My/local/path/to/feincms/media/'

4. add a url handler for feincms media files in urls.py. Again, these settings are ok on a development server, on production phase you might wanna do things differently :-)

from django.conf import settings
    urlpatterns = patterns('',
    .....
    (r'^feincms_media/(?P<path>.*)$', 'django.views.static.serve',
         {'document_root': settings.FEINCMS_ADMIN_MEDIA_LOCATION, 'show_indexes': True}),
)

5. register your hierarchical model with mptt, then remember to set the Meta option correctly.. this is needed for a correct display of the tree in the admin (obviously you need to run syncdb to create the table in the db!):

from django.db import models
import mptt

class TreeNode(models.Model):
   name = models.CharField(max_length=50, unique=True)
   parent = models.ForeignKey('self', null=True, blank=True, related_name='children')

   def __unicode__(self):
                return self.name

   class Meta:
          ordering = ['tree_id', 'lft']


mptt.register(TreeNode,)

6. create a model admin that inherits from feincms TreeEditor class:

from django.contrib import admin
from django.utils.translation import ugettext_lazy as _
from django.conf import settings as django_settings
from feincms.admin import editor
from myproject.myapp.models import *

class TreeNodeAdmin(editor.TreeEditor):
    pass

admin.site.register(TreeNode, TreeNodeAdmin)

End! That should be it! Let me know if I forgot something..
Here’s a screenshot of the new tree-management admin page we created:

UPDATE 09/2009: how to add more actions to the tree bar.
Just override the _actions_column method on the TreeNodeAdmin class, as follows::

class TreeNodeAdmin(editor.TreeEditor):
        def _actions_column(self, page):
                actions = super(TreeNodeAdmin, self)._actions_column(page)
                actions.insert(0, u'<a href="add/?parent=%s" title="%s"><img
                       src="%simg/admin/icon_addlink.gif" alt="%s"></a>' %
                       (page.pk, _('Add child page'),
                       settings.ADMIN_MEDIA_PREFIX , _('Add child page')))
               actions.insert(0, u'<a href="%s" title="%s"><img
                       src="%simg/admin/selector-search.gif" alt="%s" /></a>' %
                       (page.get_absolute_url(), _('View on site'),
                       django_settings.ADMIN_MEDIA_PREFIX, _('View on site')))
                return actions

admin.site.register(TreeNode, TreeNodeAdmin