Exception Value: Objekt vom Typ 'PolymorphicModelBase' hat keine len()

Question

Ich konvertiere bestehende Modelle/admin zu Django-polymorph. Ich denke, ich habe die Modelle und Migrationen erfolgreich gemacht (zumindest funktioniert es in der Shell), aber ich kann den Administrator nicht zum Arbeiten bringen. Ich finde die documentation ein wenig unscharf, aber ich denke, ich habe es richtig befolgt.

class LibraryItemAdmin(PolymorphicParentModelAdmin): 
    base_model = LibraryItem 
    child_models = (Whitepaper) 


class LibraryItemChildAdmin(PolymorphicChildModelAdmin): 
    base_model = LibraryItem 


class WhitepaperAdmin(LibraryItemChildAdmin): 
    form = LibraryForm 
    base_model = Whitepaper 

Ich verstehe das Problem nicht:

Traceback: 
File "/root/.virtualenvs/divesite/local/lib/python2.7/site-packages/django/core/handlers/base.py" in get_response 
    108.     response = middleware_method(request) 
File "/root/.virtualenvs/divesite/local/lib/python2.7/site-packages/django/middleware/common.py" in process_request 
    74.    if (not urlresolvers.is_valid_path(request.path_info, urlconf) and 
File "/root/.virtualenvs/divesite/local/lib/python2.7/site-packages/django/core/urlresolvers.py" in is_valid_path 
    646.   resolve(path, urlconf) 
File "/root/.virtualenvs/divesite/local/lib/python2.7/site-packages/django/core/urlresolvers.py" in resolve 
    521.  return get_resolver(urlconf).resolve(path) 
File "/root/.virtualenvs/divesite/local/lib/python2.7/site-packages/django/core/urlresolvers.py" in resolve 
    365.    for pattern in self.url_patterns: 
File "/root/.virtualenvs/divesite/local/lib/python2.7/site-packages/django/core/urlresolvers.py" in url_patterns 
    401.   patterns = getattr(self.urlconf_module, "urlpatterns", self.urlconf_module) 
File "/root/.virtualenvs/divesite/local/lib/python2.7/site-packages/django/core/urlresolvers.py" in urlconf_module 
    395.    self._urlconf_module = import_module(self.urlconf_name) 
File "/usr/lib/python2.7/importlib/__init__.py" in import_module 
    37.  __import__(name) 
File "/srv/www/urls.py" in <module> 
    349.  url(r'^admin/', include(admin.site.urls), name='admin'), 
File "/root/.virtualenvs/divesite/local/lib/python2.7/site-packages/django/contrib/admin/sites.py" in urls 
    291.   return self.get_urls(), 'admin', self.name 
File "/root/.virtualenvs/divesite/local/lib/python2.7/site-packages/django/contrib/admin/sites.py" in get_urls 
    275.     url(r'^%s/%s/' % (model._meta.app_label, model._meta.model_name), include(model_admin.urls)), 
File "/root/.virtualenvs/divesite/local/lib/python2.7/site-packages/django/contrib/admin/options.py" in urls 
    631.   return self.get_urls() 
File "/root/.virtualenvs/divesite/local/lib/python2.7/site-packages/polymorphic/admin/parentadmin.py" in get_urls 
    283.   self._lazy_setup() 
File "/root/.virtualenvs/divesite/local/lib/python2.7/site-packages/polymorphic/admin/parentadmin.py" in _lazy_setup 
    92.   self._compat_mode = len(child_models) and isinstance(child_models[0], (list, tuple)) 

Exception Type: TypeError at /admin/library 
Exception Value: object of type 'PolymorphicModelBase' has no len() 

Answer 1

Dokumentation ist veraltet. Fehlerhafte Dokumente Schlecht.

child_models sollte ein iterabler Tupel (Model, ModelAdmin) sein.

https://github.com/django-polymorphic/django-polymorphic/issues/227