Usando inversa() en Django forma

Question

Estoy tratando de utilizar la función de Django reverse() en la definición de la forma de Django para mi widget personalizado, pero estoy recibiendo un error:

ImproperlyConfigured 
The included urlconf urls doesn't have any patterns in it 

Aquí está el código:

class WorkForm(forms.Form): 
    # ... 
    category = forms.ChoiceField(
     required=True, 
     label=_('Category'), 
     help_text=_('Select most appropriate category for your work.') 
    ) 
    subcategory = forms.ChoiceField(
     widget=DependantChoiceWidget(
      default_value=_('Select category first'), 
      data_source_url=reverse('works-json-categories'), 
      # data_source_url='', -- it works this way 
      depends_on='category_id' 
     ), 
     required=True, 
     label=_('SubCategory'), 
     help_text=_('Which subcategory suits your work best.') 
    ) 

Estoy bastante seguro de que mi 'works.urls' está configurado correctamente, ya que todas las demás páginas funcionan como se esperaba.

¿Hay alguna razón por la que no puedo usar reverse() en la definición de formulario? ¿Tiene algo que ver con cuándo se ejecuta este código? ¿Hay alguna manera de solucionar esto, o la única opción aquí es codificar la URL?

Aquí está lleno de volcado de error:

Environment: 

Request Method: GET 
Request URL: http://127.0.0.1:8000/works/add?category=1&subcategory=1 

Django Version: 1.4 pre-alpha 
Python Version: 2.7.1 
Installed Applications: 
['django.contrib.auth', 
'django.contrib.contenttypes', 
'django.contrib.sessions', 
'django.contrib.sites', 
'django.contrib.messages', 
'django.contrib.staticfiles', 
'django.contrib.admin', 
'django.contrib.admindocs', 
'social_auth', 
'sorl.thumbnail', 
'helpers', 
'users', 
'works', 
'debug_toolbar'] 
Installed Middleware: 
('django.middleware.common.CommonMiddleware', 
'django.contrib.sessions.middleware.SessionMiddleware', 
'django.middleware.transaction.TransactionMiddleware', 
'django.middleware.csrf.CsrfViewMiddleware', 
'django.contrib.auth.middleware.AuthenticationMiddleware', 
'django.contrib.messages.middleware.MessageMiddleware', 
'debug_toolbar.middleware.DebugToolbarMiddleware') 


Traceback: 
File "/usr/local/lib/python2.7/dist-packages/django/core/handlers/base.py" in get_response 
    89.      response = middleware_method(request) 
File "/usr/local/lib/python2.7/dist-packages/django/middleware/common.py" in process_request 
    67.    if (not _is_valid_path(request.path_info, urlconf) and 
File "/usr/local/lib/python2.7/dist-packages/django/middleware/common.py" in _is_valid_path 
    164.   urlresolvers.resolve(path, urlconf) 
File "/usr/local/lib/python2.7/dist-packages/django/core/urlresolvers.py" in resolve 
    416.  return get_resolver(urlconf).resolve(path) 
File "/usr/local/lib/python2.7/dist-packages/django/core/urlresolvers.py" in resolve 
    298.    for pattern in self.url_patterns: 
File "/usr/local/lib/python2.7/dist-packages/django/core/urlresolvers.py" in url_patterns 
    328.   patterns = getattr(self.urlconf_module, "urlpatterns", self.urlconf_module) 
File "/usr/local/lib/python2.7/dist-packages/django/core/urlresolvers.py" in urlconf_module 
    323.    self._urlconf_module = import_module(self.urlconf_name) 
File "/usr/local/lib/python2.7/dist-packages/django/utils/importlib.py" in import_module 
    35.  __import__(name) 
File "/var/www/megenius/trunk/urls.py" in <module> 
    27.  url(r'^works/', include('works.urls')), 
File "/usr/local/lib/python2.7/dist-packages/django/conf/urls/__init__.py" in include 
    24.   urlconf_module = import_module(urlconf_module) 
File "/usr/local/lib/python2.7/dist-packages/django/utils/importlib.py" in import_module 
    35.  __import__(name) 
File "/var/www/megenius/trunk/works/urls.py" in <module> 
    2. from works.views import * 
File "/var/www/megenius/trunk/works/views.py" in <module> 
    9. from works.forms import WorkForm 
File "/var/www/megenius/trunk/works/forms.py" in <module> 
    10. class WorkForm(forms.Form): 
File "/var/www/megenius/trunk/works/forms.py" in WorkForm 
    31.    data_source_url=reverse('works-json-categories'), 
File "/usr/local/lib/python2.7/dist-packages/django/core/urlresolvers.py" in reverse 
    473.      (prefix, resolver.reverse(view, *args, **kwargs))) 
File "/usr/local/lib/python2.7/dist-packages/django/core/urlresolvers.py" in reverse 
    360.   possibilities = self.reverse_dict.getlist(lookup_view) 
File "/usr/local/lib/python2.7/dist-packages/django/core/urlresolvers.py" in reverse_dict 
    276.    self._populate() 
File "/usr/local/lib/python2.7/dist-packages/django/core/urlresolvers.py" in _populate 
    242.   for pattern in reversed(self.url_patterns): 
File "/usr/local/lib/python2.7/dist-packages/django/core/urlresolvers.py" in url_patterns 
    332.    raise ImproperlyConfigured("The included urlconf %s doesn't have any patterns in it" % self.urlconf_name) 

Exception Type: ImproperlyConfigured at /works/add 
Exception Value: The included urlconf urls doesn't have any patterns in it 

Answer 1

El problema podría ser que la forma se define antes se han cargado las direcciones URL.

Django 1.4 tendrá una función reverse_lazy que resolvería este problema. Puede implementarlo en su proyecto usted mismo (vea changeset 16121).

O bien, puede configurar el widget en su forma __init__ método en su lugar. Luego, la llamada inversa ocurre cuando se crea el formulario, después de que las URL se hayan cargado.

class WorkForm(forms.Form): 
    # ... 
    subcategory = forms.ChoiceField(
     required=True, 
     label=_('SubCategory'), 
     help_text=_('Which subcategory suits your work best.') 
    ) 
    def __init__(self, *args, **kwargs): 
     super(WorkForm, self).__init__(*args, **kwargs) 
     self.fields['subcategory'].widget=DependantChoiceWidget(
      default_value=_('Select category first'), 
      data_source_url=reverse('works-json-categories'), 
      depends_on='category_id' 
     ),