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我的 Django 项目中有两个应用程序，假设它是 appA 和 appB。这些应用程序是通过pip install. 他们两个在他们的模型中都有额外的权限：

appA 有：

  class Meta:                                                                  
      permissions = ( 
          ('clone_poll', 'Can clone poll'),                                    
          ('close_poll', 'Can close poll'),            
          ('viewresults_poll', 'Can view poll results'),                         
)

appB 有：

  class Meta:                                                                  
      permissions = ( 
          ('viewresults_meeting', 'Can view meeting results'),                         
)

我在我的项目中安装了这两个应用程序，并尝试创建他们拥有的模型的一些实例。一切正常（对象已创建并保存到数据库），直到权限分配步骤发生以下错误：

Traceback (most recent call last):
  File "/home/polls/pythonPolls/lib/python2.7/site-packages/django/core/handlers/base.py", line 114, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/home/polls/pythonPolls/lib/python2.7/site-packages/django/contrib/auth/decorators.py", line 22, in _wrapped_view
    return view_func(request, *args, **kwargs)
  File "/home/polls/pythonPolls/lib/python2.7/site-packages/polls/views.py", line 529, in clone_poll
    initial_dict=initial)(request, kwargs=kwa)
  File "/home/polls/pythonPolls/lib/python2.7/site-packages/django/views/generic/base.py", line 69, in view
    return self.dispatch(request, *args, **kwargs)
  File "/home/polls/pythonPolls/lib/python2.7/site-packages/django/contrib/formtools/wizard/views.py", line 236, in dispatch
    response = super(WizardView, self).dispatch(request, *args, **kwargs)
  File "/home/polls/pythonPolls/lib/python2.7/site-packages/django/views/generic/base.py", line 87, in dispatch
    return handler(request, *args, **kwargs)
  File "/home/polls/pythonPolls/lib/python2.7/site-packages/django/contrib/formtools/wizard/views.py", line 297, in post
    return self.render_done(form, **kwargs)
  File "/home/polls/pythonPolls/lib/python2.7/site-packages/django/contrib/formtools/wizard/views.py", line 350, in render_done
    done_response = self.done(final_form_list, **kwargs)
  File "/home/polls/pythonPolls/lib/python2.7/site-packages/polls/views.py", line 203, in done
    assign_perm('polls.change_poll', self.request.user, poll_obj)
  File "/home/polls/pythonPolls/lib/python2.7/site-packages/guardian/shortcuts.py", line 91, in assign_perm
    return model.objects.assign_perm(perm, user, obj)
  File "/home/polls/pythonPolls/lib/python2.7/site-packages/guardian/managers.py", line 41, in assign_perm
    obj_perm, created = self.get_or_create(**kwargs)
  File "/home/polls/pythonPolls/lib/python2.7/site-packages/django/db/models/manager.py", line 154, in get_or_create
    return self.get_queryset().get_or_create(**kwargs)
  File "/home/polls/pythonPolls/lib/python2.7/site-packages/django/db/models/query.py", line 380, in get_or_create
    obj.save(force_insert=True, using=self.db)
  File "/home/polls/pythonPolls/lib/python2.7/site-packages/guardian/models.py", line 44, in save
    content_type = ContentType.objects.get_for_model(self.content_object)
AttributeError: 'NoneType' object has no attribute 'objects'

我检查了发生错误的确切位置，它在 django-guardian 内部。垃圾收集器似乎清理了本地上下文，将所有导入设置为无：

'UserObjectPermissionManager': None, 
'__file__': None, 
'user_model_label': None, 
'__name__': None, 
'GroupObjectPermissionManager': None, 
'ContentType': None,
'settings': None, 
'Permission': None, 
'GroupObjectPermissionBase': None, 
'BaseObjectPermission': None,  
'UserObjectPermissionBase': None

更重要的是，当我从 INSTALLED_APPS 中删除一个应用程序（例如 appA）时，另一个工作正常，即所有权限都已设置。

我不知道这个问题的根源是什么，如果它是在我的应用程序中，在监护人中还是在完全其他应用程序中？

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1 回答 1

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经过几天的努力解决这个问题，我终于找到了解决方案，以及这个问题的真正根源。首先，我一直在使用 Django 1.6.10。在这两个应用程序中，我都为 user_logged_in 信号注册了处理程序。我将正确的函数和绑定（user_logged_in.connect(handler)) 放入两个应用程序中名为 signals.py 的文件中。然后在 __init__.py 中导入 signals.py，以使信号连接正常工作。在其中一个文件中还存在对 models.py 的另一种依赖关系，该文件也被导入到 signals.py 中——这是在其中一个应用程序中完成的。直截了当，问题在于其中一个应用程序中的循环导入。我发现可行的解决方案是将信号.py 内容移动到模型.py，从 __init__.py 中删除信号导入。

于 2015-07-31T13:37:52.520 回答