1

从 Django 1.6.5 升级到 1.7 后，我的视图抛出以下错误：

ValueError at /mrp/manage/materials/ dictionary update sequence element #0 has length 12; 2 is required

断点在render我在视图函数中返回的函数上：

def manage_materials(request):
    context = dict()
    context['material_list'] = Material.objects.order_by('material_type', 'name')
    return render(request, 'erp/mrp/manage_materials.html',
                  RequestContext(request, context))

在我的代码中似乎是一个普遍的错误，每次调用都会render触发这个错误。

完整的堆栈跟踪

Environment:


Request Method: GET
Request URL: http://localhost:8000/mrp/manage/materials/

Django Version: 1.7
Python Version: 3.4.1
Installed Applications:
('django.contrib.admin',
 'django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.messages',
 'django.contrib.staticfiles',
 'erp')
Installed Middleware:
('django.contrib.sessions.middleware.SessionMiddleware',
 'django.middleware.common.CommonMiddleware',
 'django.middleware.csrf.CsrfViewMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware',
 'django.middleware.clickjacking.XFrameOptionsMiddleware')


Traceback:
File "C:\Python34\lib\site-packages\django\core\handlers\base.py" in get_response
  111.                     response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "C:\Python34\lib\site-packages\django\contrib\auth\decorators.py" in _wrapped_view
  22.                 return view_func(request, *args, **kwargs)
File "D:\app\ecerp\erp\views\mrp.py" in manage_materials
  125.                   RequestContext(request, context))
File "C:\Python34\lib\site-packages\django\shortcuts.py" in render
  48.     return HttpResponse(loader.render_to_string(*args, **kwargs),
File "C:\Python34\lib\site-packages\django\template\loader.py" in render_to_string
  177.     with context_instance.push(dictionary):
File "C:\Python34\lib\site-packages\django\template\context.py" in push
  54.         return ContextDict(self, *args, **kwargs)
File "C:\Python34\lib\site-packages\django\template\context.py" in __init__
  19.         super(ContextDict, self).__init__(*args, **kwargs)

Exception Type: ValueError at /mrp/manage/materials/
Exception Value: dictionary update sequence element #0 has length 12; 2 is required

有谁知道为什么？

4

1 回答 1

3

这是因为render()快捷方式将自动应用于RequestContext上下文。在 django 1.6 中，调用是合法的：

def myview(request):
    context = {'my_var': 'my_value'}
    return render(request, 'erp/mrp/manage_materials.html',
              RequestContext(request, context))

它将 aRequestContext作为render()函数的第三个参数。

这实际上是没有必要的（看到request对象在那里被传递了两次）。快捷函数将创建一个 RequestContext 对象，该render()对象可以从周围的请求中获取上下文。

因此，有两种解决方案可以解决此错误：

  1. 将第三个参数的名称显式设置RequestContet(...)为context_instance：

    return render(request, 'erp/mrp/manage_materials.html', context_instance=RequestContext(request, context))

  2. 只需使用dict上下文作为第三个参数：

    返回渲染（请求，'erp/mrp/manage_materials.html'，上下文）

第二个更好看。

笔记：

render()关于快捷功能的文档之间没有区别：

1.7 文档：https ://docs.djangoproject.com/en/1.7/topics/http/shortcuts/#render

1.6 文档：https ://docs.djangoproject.com/en/1.6/topics/http/shortcuts/#render

于 2014-09-27T08:11:25.827 回答