Select a subset of foreign key elements in inlineformset_factory in Django

I have a model with two foreign keys:

class Model1(models.Model):
  model_a = models.ForeignKey(ModelA)
  model_b = models.ForeignKey(ModelB)
  value = models.IntegerField()

Then, I create an inline formset class, like so:

an_inline_formset = inlineformset_factory(ModelA, Model1, fk_name="model_a")

and then instantiate it, like so:

a_formset = an_inline_formset(request.POST, instance=model_A_object)

Once this formset gets rendered in a template/page, there is ChoiceField associated with the model_b field. The problem I'm having is that th开发者_StackOverflow社区e elements in the resulting drop down menu include all of the elements found in ModelB table. I need to select a subset of those based on some criteria from ModelB. At the same time, I need to keep the reference to the instance of model_A_object when instantiating inlineformset_factory and, therefore, I can't just use this example. Any suggestions?

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What you need to do is change the ModelChoiceField's queryset

The easiest way to do this may be to monkey-patch the formset's form. You should be able to do this right after constructing the formset with:

an_inline_formset.form.base_fields['model_b'].queryset = ModelB.objects.filter(whatever=True)

Not the prettiest, but it should work.