Django Rest Framework filtering a field with null and multiple values-CodePudding

I am using Django Rest Framework and want to filter the queryset in a view based on a certain field name.

The filter values would be null and additionally any other particular value for the field blog_category which is a ForeignKey value. So filter query should be on two query params

class Blog(ListCreateAPIView):
    permission_classes = [DjangoCustomModelPermissions]
    queryset = Blog.objects.all().select_related("blog_category")
    serializer_class = Blog_Serializer
    pagination_class = CustomPageNumberPagination
    filterset_fields = {'blog_category': ['isnull', 'exact', 'in']}

I have added the lookup fields isnull to filter null values

I have tried the following url requests but they do not work

/blog/?blog_catgeory__in=1,null
/blog/?blog_catgeory__in=1,isnull
/blog/?blog_catgeory__in=1,isnull=true
/blog/?blog_catgeory__in=1&blog_category__isnull=true

How do I get this work?

Edit After answer Javohir Elmurodov's answer

I made the following modifications but it still does not work

class NumberInFilter(django_filters.BaseInFilter, django_filters.NumberFilter):
    pass


class BlogFilter(filters.FilterSet):
    blog_category = NumberInFilter(field_name='blog_category', lookup_expr='in')
    blog_category__isnull = BooleanFilter(
        field_name='blog_category', lookup_expr='isnull')


class Blog_ListView(ListData, CreateData, CustomGenericAPIView):
    permission_classes = [DjangoCustomModelPermissions]
    queryset = Blog.objects.all().select_related("blog_category")
    serializer_class = Blog_Serializer
    pagination_class = CustomPageNumberPagination
    filterset_class = BlogFilter

I tried the following links

/blog/?blog_catgeory=1&blog_category__isnull
/blog/?blog_catgeory=1&blog_category__isnull=true

Still does not work

I want to search for all entries in queryset that are null OR a particular value in blog_category

CodePudding user response：

It’s not always appropriate to directly match a filter to its model field’s type, as some lookups expect different types of values. This is a commonly found issue with in, range, and isnull lookups.

While the underlying column type for category is an integer, isnull lookups expect a boolean value.

You can check in Filter and lookup expression mismatch (in, range, isnull)

CodePudding user response：

The above problem can be solved by overriding the filter method

from django.db.models import Q
from django_filters import rest_framework as filters
from django_filters import CharFilter

class BlogFilter(filters.FilterSet):
    blog_category = CharFilter(field_name='blog_category_mast',
                               lookup_expr='exact',method='include_null')

    def include_null(self, queryset, name, value):
        return queryset.filter(
            Q(**{f'{name}__isnull': True}) | Q(**{name: value})
        )


class Blog(ListCreateAPIView):
    permission_classes = [DjangoCustomModelPermissions]
    queryset = Blog.objects.all().select_related("blog_category")
    serializer_class = Blog_Serializer
    pagination_class = CustomPageNumberPagination
    filterset_class = BlogFilter