Django 在 ModelChoiceField 上形成 keyerror

Question

我有一个用于高级搜索的表单。其中一个字段，island_group 是一个 ModelChoiceField，我为其返回一个 values_list 作为查询集（以便只获取每个不同的值一次）。

forms.py：

class SearchForm(forms.Form):
    ...
    island_group = forms.ModelChoiceField(
        required=False,
        queryset=Locality.objects.values_list('islandgroup', flat=True).distinct('islandgroup')
    ...

因为这会引发invalid choice 的错误，因为我使用的是值而不是对象，所以我覆盖了错误：

    def clean(self):
        cleaned_data = super(SearchForm, self).clean()

        if self._errors["island_group"]:
            del self._errors["island_group"]

        return cleaned_data

但是，我不断收到KeyError at /collections/ 'island_group' 错误。事实上，由于这些数据是从只读数据库中提取的，我只是希望能够以最小的麻烦将其传递到视图中。

任何帮助将不胜感激。另外，这是回溯：

Traceback:
File "/home/sam/django-projects/datazone/local/lib/python2.7/site-packages/django/core/handlers/base.py" in get_response
  111.                         response = callback(request, *callback_args, **callback_kwargs)
File "/home/sam/django-projects/datazone/bin/datazone/cdrs/views.py" in cdrs_index
  59.     return render(request, 'cdrs_index.html', context)    
File "/home/sam/django-projects/datazone/local/lib/python2.7/site-packages/django/shortcuts/__init__.py" in render
  44.     return HttpResponse(loader.render_to_string(*args, **kwargs),
File "/home/sam/django-projects/datazone/local/lib/python2.7/site-packages/django/template/loader.py" in render_to_string
  188.         return t.render(context_instance)
File "/home/sam/django-projects/datazone/local/lib/python2.7/site-packages/django/template/base.py" in render
  123.             return self._render(context)
File "/home/sam/django-projects/datazone/local/lib/python2.7/site-packages/django/test/utils.py" in instrumented_test_render
  57.     return self.nodelist.render(context)
File "/home/sam/django-projects/datazone/local/lib/python2.7/site-packages/django/template/base.py" in render
  744.                 bits.append(self.render_node(node, context))
File "/home/sam/django-projects/datazone/local/lib/python2.7/site-packages/django/template/base.py" in render_node
  757.         return node.render(context)
File "/home/sam/django-projects/datazone/local/lib/python2.7/site-packages/django/template/loader_tags.py" in render
  127.         return compiled_parent._render(context)
File "/home/sam/django-projects/datazone/local/lib/python2.7/site-packages/django/test/utils.py" in instrumented_test_render
  57.     return self.nodelist.render(context)
File "/home/sam/django-projects/datazone/local/lib/python2.7/site-packages/django/template/base.py" in render
  744.                 bits.append(self.render_node(node, context))
File "/home/sam/django-projects/datazone/local/lib/python2.7/site-packages/django/template/base.py" in render_node
  757.         return node.render(context)
File "/home/sam/django-projects/datazone/local/lib/python2.7/site-packages/django/template/loader_tags.py" in render
  64.             result = block.nodelist.render(context)
File "/home/sam/django-projects/datazone/local/lib/python2.7/site-packages/django/template/base.py" in render
  744.                 bits.append(self.render_node(node, context))
File "/home/sam/django-projects/datazone/local/lib/python2.7/site-packages/django/template/base.py" in render_node
  757.         return node.render(context)
File "/home/sam/django-projects/datazone/local/lib/python2.7/site-packages/django/template/defaulttags.py" in render
  227.                 nodelist.append(node.render(context))
File "/home/sam/django-projects/datazone/local/lib/python2.7/site-packages/django/template/base.py" in render
  792.             output = self.filter_expression.resolve(context)
File "/home/sam/django-projects/datazone/local/lib/python2.7/site-packages/django/template/base.py" in resolve
  510.                 obj = self.var.resolve(context)
File "/home/sam/django-projects/datazone/local/lib/python2.7/site-packages/django/template/base.py" in resolve
  653.             value = self._resolve_lookup(context)
File "/home/sam/django-projects/datazone/local/lib/python2.7/site-packages/django/template/base.py" in _resolve_lookup
  683.                         current = getattr(current, bit)
File "/home/sam/django-projects/datazone/local/lib/python2.7/site-packages/django/forms/forms.py" in _errors
  415.         return self.form.errors.get(self.name, self.form.error_class())
File "/home/sam/django-projects/datazone/local/lib/python2.7/site-packages/django/forms/forms.py" in _get_errors
  112.             self.full_clean()
File "/home/sam/django-projects/datazone/local/lib/python2.7/site-packages/django/forms/forms.py" in full_clean
  268.         self._clean_form()
File "/home/sam/django-projects/datazone/local/lib/python2.7/site-packages/django/forms/forms.py" in _clean_form
  296.             self.cleaned_data = self.clean()
File "/home/sam/django-projects/datazone/bin/datazone/cdrs/forms.py" in clean
  113.         if self._errors["island_group"]:

Exception Type: KeyError at /collections/
Exception Value: 'island_group'

Answer 1

更新

我想我知道你的例外情况，它可能看起来像 Select a valid choice. That choice is not one of the available choices. 对吧？ 原因是您传递给queryset= 的Locality.objects.values_list('islandgroup', flat=True).distinct('islandgroup') 是ValuesListQuerySet 而不是QuerySet。 ValueListQuerySet 实例不包含_meta 信息并用作普通列表，这会导致ModelChoiceField 生成错误的表单选项。就像下面这个人为的例子

>>> from django import forms
>>> from django.contrib.auth.models import *

>>> class F(forms.Form):
...     user = forms.ModelChoiceForm(queryset=User.objects.values_list('username', flat=True))

>>> print F().as_p()
<p><label for="id_user">User:</label> <select name="user" id="id_user">
<option value="" selected="selected">---------</option>
<option value="okm">okm</option>
</select></p>

但是，第二个选项的正确值应该是用户okm的pk，就像

>>> class F(forms.Form):
...     user = forms.ModelChoiceForm(queryset=User.objects)

>>> print F().as_p()
<p><label for="id_user">User:</label> <select name="user" id="id_user">
<option value="" selected="selected">---------</option>
<option value="1">okm</option>
</select></p>

因此您需要根据islandgroup 模型字段的类型更改代码中的island_group = 行。

除了上面的问题，你的代码都很好。因此，当self._errors 中没有其他'island_group' 验证错误时，self._errors["island_group"] 会引发 KeyError。