Make field's queryset from cleaned_data

Question

How can you make a queryset or a list from cleaned data without accessing the database? I'm using Django 1.5 FormWizard and ModelFormSet here. The following doesn't work with the error:

'list' object has no attribute 'all'

That means you can't use a list, can you?

def get_form(self, step=None, data=None, files=None):
    form = super(MyWizard, self).get_form(step=step, data=data, files=files)
    #...
    data = self.get_cleaned_data_for_step('a')
    list = []
    for item in data:
        list.append(item['car']) # This is the choice of a ForeigenKey
    #...
    form.fields['name'].queryset = list

This is working but it seems to me that you do the work twice:

def get_form(self, step=None, data=None, files=None):
    form = super(MyWizard, self).get_form(step=step, data=data, files=files)
    #...
    data = self.get_cleaned_data_for_step('a')
    list = []
    for item in data:
        list.append(item['car'].id) # This is the choice of a ForeigenKey
    #...
    form.fields['name'].queryset = SomeClass.objects.filter(pk__in=list)

So is there a way around?

Answer 1

You can't use a list in place of a queryset, you have to assign a queryset to the fields queryset attribute, hence the first error. You have to hit the DB to make the queryset, so I'm not sure what you're asking. You could improve the code by using a list comp:

my_list = [item['car'].id for item in data]

Answer 2

Perhaps you can post your form declaration, but it seems that name is a ModelChoiceField, and thus requires a queryset. You could convert it to a simple ChoiceField, but you would have to build the choices:

form.fields['name'].choices = [(item['car'].id, unicode(item['car'])] for item in data]

However, I'm not sure if this would save automatically, in case this is a ModelForm, but then again, we would need the form declaration to tell.