Overriding the save() method of a model that uses django-mptt
- by saturdayplace
I've been using django-mptt in my project for a while now, it's fabulous. Recently, I've found a need to override a model's save() method that uses mptt, and I'm getting an error when I try to save a new instance of that model:
Exception Type: ValueError at /admin/scrivener/page/add/
Exception Value: Cannot use None as a query value
I'm assuming that this is a result of the fact that the instance hasn't been stuck into a tree yet, but I'm not sure how to go about fixing this. I added a comment about it onto a similar issue on the project's tracker, but I was hoping that someone here might be able to put me on the right track faster.
Here's the traceback.
Environment:
Request Method: POST
Request URL: http://localhost:8000/admin/scrivener/page/add/
Django Version: 1.2 rc 1 SVN-13117
Python Version: 2.6.4
Installed Applications:
['django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.sites',
'django.contrib.admin',
'django.contrib.sitemaps',
'mptt',
'filebrowser',
'south',
'haystack',
'django_static',
'etc',
'scrivener',
'gregor',
'annunciator']
Installed Middleware:
('django.middleware.common.CommonMiddleware',
'django.contrib.sessions.middleware.SessionMiddleware',
'django.contrib.auth.middleware.AuthenticationMiddleware')
Traceback:
File "B:\django-apps\3rd Party Source\django\core\handlers\base.py" in get_response
100. response = callback(request, *callback_args, **callback_kwargs)
File "B:\django-apps\3rd Party Source\django\contrib\admin\options.py" in wrapper
239. return self.admin_site.admin_view(view)(*args, **kwargs)
File "B:\django-apps\3rd Party Source\django\utils\decorators.py" in _wrapped_view
74. response = view_func(request, *args, **kwargs)
File "B:\django-apps\3rd Party Source\django\views\decorators\cache.py" in _wrapped_view_func
69. response = view_func(request, *args, **kwargs)
File "B:\django-apps\3rd Party Source\django\contrib\admin\sites.py" in inner
190. return view(request, *args, **kwargs)
File "B:\django-apps\3rd Party Source\django\utils\decorators.py" in _wrapper
21. return decorator(bound_func)(*args, **kwargs)
File "B:\django-apps\3rd Party Source\django\utils\decorators.py" in _wrapped_view
74. response = view_func(request, *args, **kwargs)
File "B:\django-apps\3rd Party Source\django\utils\decorators.py" in bound_func
17. return func(self, *args2, **kwargs2)
File "B:\django-apps\3rd Party Source\django\db\transaction.py" in _commit_on_success
299. res = func(*args, **kw)
File "B:\django-apps\3rd Party Source\django\contrib\admin\options.py" in add_view
795. self.save_model(request, new_object, form, change=False)
File "B:\django-apps\3rd Party Source\django\contrib\admin\options.py" in save_model
597. obj.save()
File "B:\django-apps\scrivener\models.py" in save
205. self.url = self.get_absolute_url()
File "B:\django-apps\3rd Party Source\django\utils\functional.py" in _curried
55. return _curried_func(*(args+moreargs), **dict(kwargs, **morekwargs))
File "B:\django-apps\3rd Party Source\django\db\models\base.py" in get_absolute_url
940. return settings.ABSOLUTE_URL_OVERRIDES.get('%s.%s' % (opts.app_label, opts.module_name), func)(self, *args, **kwargs)
File "B:\django-apps\3rd Party Source\django\db\models\__init__.py" in inner
31. bits = func(*args, **kwargs)
File "B:\django-apps\scrivener\models.py" in get_absolute_url
194. for ancestor in self.get_ancestors():
File "B:\django-apps\3rd Party Source\mptt\models.py" in get_ancestors
23. opts.tree_id_attr: getattr(self, opts.tree_id_attr),
File "B:\django-apps\3rd Party Source\django\db\models\manager.py" in filter
141. return self.get_query_set().filter(*args, **kwargs)
File "B:\django-apps\3rd Party Source\django\db\models\query.py" in filter
550. return self._filter_or_exclude(False, *args, **kwargs)
File "B:\django-apps\3rd Party Source\django\db\models\query.py" in _filter_or_exclude
568. clone.query.add_q(Q(*args, **kwargs))
File "B:\django-apps\3rd Party Source\django\db\models\sql\query.py" in add_q
1131. can_reuse=used_aliases)
File "B:\django-apps\3rd Party Source\django\db\models\sql\query.py" in add_filter
1000. raise ValueError("Cannot use None as a query value")
Exception Type: ValueError at /admin/scrivener/page/add/
Exception Value: Cannot use None as a query value
