Filtering Django queryset with custom function - django

Question

I'm developing a REST API for an existing system that uses custom permission handling. I'm attempting to use the built-in generics from the Django REST Framework, but I'm running into trouble filtering the list views using my custom permissions. An example of my current view is:
class WidgetList(generics.ListCreateAPIView):
permission_classes = (permissions.IsAuthenticated,)
model = Widget
serializer_class = WidgetSerializer
filter_backends = (filters.DjangoFilterBackend,)
filter_fields = ('widget_type', 'widget_owner')
def get_queryset(self):
"""
Overwrite the query set to check permissions
"""
qs_list = [w.id for w in self.model.objects.all() if
canReadWidget(self.request.user, w)]
return self.model.objects.filter(id__in=qs_list)
This works, however I feel like the get_queryset function could be improved. Because my canReadWidget is custom, I have to evaluate self.model.objects.all() and check which widgets the user can read, but the function must return a query set so I use the id__in=qs_list part. The result being that I make two database calls for what is really just one list fetch.
Is there a standard way to handle this kind of per-object filtering for a generic list view?

Answer 1

At some point, it's better to drop the default generic views or function and roll your own.
You should have a look at the ListModelMixin and override the list to deal with the list instead of turning it into a queryset.
You should adapt the filtering and pagination but you won't hit the DB twice as you currently do.

Answer 2

first install django-filter package and register in settings.py
Write this code on filter.py file
import django_filters
from .models import CustomUser
class UserFilter(django_filters.FilterSet):
first_name = django_filters.CharFilter(label="First Name", lookup_expr='icontains')
last_name = django_filters.CharFilter(label="Last Name", lookup_expr='icontains')
email = django_filters.CharFilter(label="Email", lookup_expr='icontains')
mobile_number = django_filters.CharFilter(label="Mobile No.", lookup_expr='icontains')
##Change Your Fields What You Want To Filtering
class Meta:
model = Widget
fields = {'is_verify'}
On Your Views File write this code:
class WidgetViewSet(MyModelViewSet):
queryset = Widget.objects
serializer_class = "pass your serializer"
def get_filter_data(self):
_data = self.queryset.all()
data = UserFilter(self.request.GET, queryset=_data)
return data.qs.order_by('-id')
def get_queryset(self):
return self.get_filter_data()