Django在ModelChoiceField上形成keyerror

Question

我有一個用於高級搜索的表單。其中一個字段island_group是一個ModelChoiceField，爲此我返回一個values_list作爲查詢集（以便只獲取一次不同的值）。

forms.py：

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

因爲這將引發沿invalid choice行的錯誤，因爲我使用的值，而不是對象，我重寫了錯誤：

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

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

     return cleaned_data 

但是，我不斷收到KeyError at /collections/ 'island_group'錯誤。實際上，這些數據是從一個只讀數據庫中提取的，我只是希望能夠以最小的麻煩將它傳遞給視圖。

任何幫助將不勝感激。另外，這裏是回溯：

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，它可能看起來像Select a valid choice. That choice is not one of the available choices.吧？ 原因是您傳遞給queryset=的Locality.objects.values_list('islandgroup', flat=True).distinct('islandgroup')是ValuesListQuerySet而不是QuerySet。 ValueListQuerySet實例不包含_meta信息並用作普通列表，這會導致ModelChoiceField生成不正確的表單選項。就像下面

>>> 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> 

的人爲的例子。然而，第二個選項的正確值應該是用戶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，您需要更改island_group =線在你的代碼，根據islandgroup模型字段的類型。

除了上面的問題，你的代碼是好的。因此，如果self._errors中沒有其他'island_group'驗證錯誤，則self._errors["island_group"]會引發KeyError錯誤。