forms ModelChoiceField queryset + extra choice fields django forms

Question

I am trying to create a form in that ModelChoiceField loads from queryset and i want add few custom values to ModelChoiceField for extend i have used choice field, like below but while updating the form,getting below error

Form Error : Select a valid choice. That choice is not one of the available choices.

Code :

 self.fields['lead'] = forms.ModelChoiceField(queryset = Pepole.objects.filter(poc__in       = ('lead','sr.lead')))
 self.fields['lead2'] = forms.ModelChoiceField(queryset = Pepole.objects.filter(role__in = ('lead','sr.lead')))
      choice_field = self.fields['lead']                                    
      choice_field.choices = list(choice_field.choices) + [('None', 'None')]
      choice_field = self.fields['lead2']                                    
      choice_field.choices = list(choice_field.choices) + [('None', 'None')]

Am i doing any thing wrong here?

Answer 1

That's not going to work. Look at how a ModelChoiceField works:

try:
    key = self.to_field_name or 'pk'
    value = self.queryset.get(**{key: value})
except self.queryset.model.DoesNotExist:
    raise ValidationError(self.error_messages['invalid_choice'])
return value

You can't add something randomly to it.

Use a ChoiceField instead and custom process the data.

class TestForm(forms.Form):
    mychoicefield = forms.ChoiceField(choices=QS_CHOICES)

    def __init__(self, *args, **kwargs):
        super(TestForm, self).__init__(*args, **kwargs)
        self.fields['mychoicefield'].choices = \
            list(self.fields['mychoicefield'].choices) + [('new stuff', 'new')]

    def clean_mychoicefield(self):
        data = self.cleaned_data.get('mychoicefield')
        if data in QS_CHOICES:
            try:
                data = MyModel.objects.get(id=data)
            except MyModel.DoesNotExist:
                raise forms.ValidationError('foo')
        return data