How to dynamically set the queryset of a models.ModelChoiceField on a forms.Form subclass

Question

The constructor for forms.ModelChoiceField requires a queryset. I do not know the queryset until the request happens. Distilled:

# models.py class Bar(models.model):     text = models.TextField()  class Foo(models.Model):     name = models.CharField()     bar = models.ForeignKey(Bar)  # forms.py class FooForm(forms.Form):     name = forms.CharField()     text = forms.CharField(widget=forms.TextArea)      bar = forms.ModelChoiceField(queryset='??????') 

What I am currently doing:

# forms.py  def get_foo_form_class(bars_queryset):     class FooForm(forms.Form):         name = forms.CharField()         text = forms.CharField(widget=forms.TextArea)          bar = forms.ModelChoiceField(queryset=bars_queryset)      return FooForm 

I can then call it in the view using arguments parsed out of the url with a urlconf to construct the queryset and get the class. This feels like the wrong way to do it. Is there an established way to do this in django?

Answer 1

Override the form's __init__ method and set the queryset there.

class FooForm(forms.Form):     bar = forms.ModelChoiceField(queryset=Bar.objects.none())      def __init__(self, *args, **kwargs):         qs = kwargs.pop('bars')         super(FooForm, self).__init__(*args, **kwargs)         self.fields['bar'].queryset = qs