How to apply a filter backend to all fields of all resources in Django Rest Framework?

Right now you are telling Django REST Framework to use the DjangoFilterBackend for all views, but you are not telling it how the FilterSet should be generated.

---

django-filter will automatically generate a FilterSet for all of the fields on a model if the fields are set to None. Django REST Framework will automatically generate a FilterSet if filter_fields are not set to None, which means you won't be able to use the default DjangoFilterBackend.

You can create a custom DjangoFilterBackend though, which will automatically generate the FilterSet for all fields on the model.

from rest_framework.filters import DjangoFilterBackend

class AllDjangoFilterBackend(DjangoFilterBackend):
    """
    A filter backend that uses django-filter.
    """

    def get_filter_class(self, view, queryset=None):
        """
        Return the django-filters `FilterSet` used to filter the queryset.
        """
        filter_class = getattr(view, 'filter_class', None)
        filter_fields = getattr(view, 'filter_fields', None)

        if filter_class or filter_fields:
            return super(AllDjangoFilterBackend, self).get_filter_class(self, view, queryset)

        class AutoFilterSet(self.default_filter_set):
            class Meta:
                model = queryset.model
                fields = None

        return AutoFilterSet

This will still use the original filter backend for situations where the view defines a custom filter_class or filter_fields, but it will generate a custom FilterSet for all other situations. Keep in mind that you shouldn't allow fields which aren't returned through the API to be filtered, as you are opening yourself up to future security issues (like people filtering a user list by passwords).