Question

非常简单的代码，但奇怪的情况......

有一个包含此代码段的模板：

{% is_contest story as iscontest %}

其中is_contest是此自定义模板标记：

@register.assignment_tag
def is_contest(obj):
    contesttype = ContentType.objects.get_for_model(Contest)
    return obj.source_content_type == contesttype

但是竞赛在django_content_type表中。

最奇怪的部分：这只是一个间歇性的错误，而且似乎只是由模板标签引起的（我也会检查视图，但没有错误）。

有什么想法吗？

编辑：完全追溯

Traceback (most recent call last):

  File "/usr/local/lib/python2.7/dist-packages/django/core/handlers/base.py", line 111, in get_response
    response = callback(request, *callback_args, **callback_kwargs)

  File "/home/ubuntu/src/cbframe/commentableobjects/views/commentableobject_list.py", line 142, in commentablobject_list
    return render_to_response('commentableobjects-list.html', info, context_instance=RequestContext(request))

  File "/usr/local/lib/python2.7/dist-packages/django/shortcuts/__init__.py", line 20, in render_to_response
    return HttpResponse(loader.render_to_string(*args, **kwargs), **httpresponse_kwargs)

  File "/usr/local/lib/python2.7/dist-packages/django/template/loader.py", line 176, in render_to_string
    return t.render(context_instance)

  File "/usr/local/lib/python2.7/dist-packages/django/template/base.py", line 140, in render
    return self._render(context)

  File "/usr/local/lib/python2.7/dist-packages/django/template/base.py", line 134, in _render
    return self.nodelist.render(context)

  File "/usr/local/lib/python2.7/dist-packages/django/template/base.py", line 823, in render
    bit = self.render_node(node, context)

  File "/usr/local/lib/python2.7/dist-packages/django/template/debug.py", line 74, in render_node
    return node.render(context)

  File "/usr/local/lib/python2.7/dist-packages/django/template/loader_tags.py", line 123, in render
    return compiled_parent._render(context)

  File "/usr/local/lib/python2.7/dist-packages/django/template/base.py", line 134, in _render
    return self.nodelist.render(context)

  File "/usr/local/lib/python2.7/dist-packages/django/template/base.py", line 823, in render
    bit = self.render_node(node, context)

  File "/usr/local/lib/python2.7/dist-packages/django/template/debug.py", line 74, in render_node
    return node.render(context)

  File "/usr/local/lib/python2.7/dist-packages/django/template/loader_tags.py", line 62, in render
    result = block.nodelist.render(context)

  File "/usr/local/lib/python2.7/dist-packages/django/template/base.py", line 823, in render
    bit = self.render_node(node, context)

  File "/usr/local/lib/python2.7/dist-packages/django/template/debug.py", line 74, in render_node
    return node.render(context)

  File "/usr/local/lib/python2.7/dist-packages/django/template/defaulttags.py", line 281, in render
    return nodelist.render(context)

  File "/usr/local/lib/python2.7/dist-packages/django/template/base.py", line 823, in render
    bit = self.render_node(node, context)

  File "/usr/local/lib/python2.7/dist-packages/django/template/debug.py", line 74, in render_node
    return node.render(context)

  File "/usr/local/lib/python2.7/dist-packages/django/template/loader_tags.py", line 155, in render
    return self.render_template(self.template, context)

  File "/usr/local/lib/python2.7/dist-packages/django/template/loader_tags.py", line 137, in render_template
    output = template.render(context)

  File "/usr/local/lib/python2.7/dist-packages/django/template/base.py", line 140, in render
    return self._render(context)

  File "/usr/local/lib/python2.7/dist-packages/django/template/base.py", line 134, in _render
    return self.nodelist.render(context)

  File "/usr/local/lib/python2.7/dist-packages/django/template/base.py", line 823, in render
    bit = self.render_node(node, context)

  File "/usr/local/lib/python2.7/dist-packages/django/template/debug.py", line 74, in render_node
    return node.render(context)

  File "/usr/local/lib/python2.7/dist-packages/django/template/defaulttags.py", line 185, in render
    nodelist.append(node.render(context))

  File "/usr/local/lib/python2.7/dist-packages/django/template/base.py", line 1139, in render
    context[self.target_var] = func(*resolved_args, **resolved_kwargs)

  File "/home/ubuntu/src/cbframe/commentableobjects/templatetags/url_target_blank.py", line 27, in is_contest
    return obj.source_content_type == contesttype

  File "/usr/local/lib/python2.7/dist-packages/django/db/models/fields/related.py", line 350, in __get__
    rel_obj = qs.get(**params)

  File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 366, in get
    % self.model._meta.object_name)

DoesNotExist: ContentType matching query does not exist.

Answer 1

一个问题可能是您正在将2个实例与彼此进行比较，而Django中的这些实例应该是相同的，因为Django会对它们进行缓存，这不是保证。

不确定source_content_type的来源/位置，但我建议改为：

return isinstance(obj, contesttype)

至于原来的问题，你有堆栈跟踪吗？这个错误似乎有点奇怪。

您确定Contest未在范围内的某处被覆盖吗？ Contest可能被模块中的其他代码覆盖，在这种情况下最可能的怀疑是global Contest，但这似乎不是这种情况。

[编辑]

感谢堆栈跟踪，问题更加清晰。

这一部分明确表明它在obj.source_content_type部分出错：

return obj.source_content_type == contesttype

我认为某个对象不再存在source_content_type。

“DoesNotExist：ContentType匹配查询不存在”只是偶尔发生

1 个答案: