Negative custom Django admin FilterSpec

Question

I'm working on a custom Django Admin FilterSpec (covered already on SO #991926). My FilterSpec is a replacement for the default filter on ForeignKey(User), and basically replaces the list of all users with three only choices, all, mine, and others.

For example, if I applied the custom filterspec to the field created_by it would add an admin filter with All, Created by Me, and Created by Others. Everything works except the negative filter, Created by Others.

I've been attempting to achieve this by appending __not to the query as so:

def choices(self, cl):
    yield {
            'selected': self.lookup_val == self.user.pk,
            'query_string': cl.get_query_string({'%s__not' % self.field.name: self.user.pk}),
            'display': capfirst('%s Others' % self.field.verbose_name)
        }

It doesn't seem that Django supports filtering in the negative like this. I've also experimented with having it do a __gte and __lte but the filterspec only uses the first one it finds (gte), dropping the other (lte).

Anybody know how to achieve a negative filter like this through a custom FilterSpec?

Answer 1

Won't using a "exclude" filter for the negation work?

Answer 2

This feature is not part of the Django code yet; it is planned for version 1.2. You'll need to apply this patch to the Django code: http://code.djangoproject.com/ticket/5833

Use the get_query_set() method of FilterSpec. For example:

class AlunoStatus(FilterSpec):
    def __init__(self, request, params, model, model_admin):
        self.lookup_val = request.GET.get('exclude_value', None)

    def get_query_set(self, cl, qs):
        if self.lookup_val:
            qs = qs.exclude(field=self.lookup_val)
        return qs

    def choices(self, cl):
        yield {'selected': self.lookup_val is None,
               'query_string': cl.get_query_string({}, ['exclude_value']),
               'display': _('All')}
        for choice in choices:
            yield {'selected': self.lookup_val == choice,
                    'query_string': cl.get_query_string({'exclude_value': choice}),
                    'display': u"Exclude "+smart_unicode(choice)}

I didn't test this, but I hope you get the idea.