How to filter the values of two fields as one? - django-filter

Question

How to aggregate the results of the two fields and show as one in django-filter?
Let's take, for example, such a model:
class Animal(object):
LEGS_CHOICES = (2, 4, 8)
legs = models.PositiveSmallIntegerField(choices=LEGS_CHOICES)
class Dog(Animal):
pass
class Spider(Animal):
pass
My django-filter filter class:
class AnimalFilterSet(django_filters.FilterSet):
legs = django_filters.MultipleChoiceFilter(choices=Animal.LEGS_CHOICES, widget=forms.CheckboxSelectMultiple())
class Meta:
model = Animal
fields = ['legs']
I would like to filter this two models by the same fields and display them as one.
Using queryset I can do it like this:
Animal.objects.filter(Q(dog__legs = 4) | Q(spider__legs = 4))

Answer 1

I wrote my own Filter
class MultiMultipleChoiceFilter(django_filters.Filter):
"""
This filter preforms an OR query on the selected options for defined fields.
"""
field_class = forms.MultipleChoiceField
def __init__(self, fields, *args, **kwargs):
super(MultiMultipleChoiceFilter, self).__init__(*args, **kwargs)
self.fields = fields
def filter(self, qs, value):
value = value or ()
if len(value) == len(self.field.choices):
return qs
q = Q()
for v in value:
for f in self.fields:
q |= Q(**{f: v})
return qs.filter(q).distinct()
Example of use. As a parameter, enter a list of fields.
class AnimalFilterSet(django_filters.FilterSet):
legs = django_filters.MultiMultipleChoiceFilter(['dog__legs', 'spider__legs'], choices=Animal.LEGS_CHOICES, widget=forms.CheckboxSelectMultiple())
class Meta:
model = Animal
fields = ['legs']