MultipleObjectsReturned error in Django but I want multiple objects to be returned

Question

Using Django REST framework I created an url which maps to a page with a JSON file containing all the objects in my database.

I want to do the same but instead of showing all the objects I want only the objects that match a specific category (category is an attribute in my model).

I have urls that show a JSON files with a single object in it (using the pk attribute) but when I try to do the same thing with category instead of pk I get a MultipleObjectsReturned error.

I'm just sperimenting with the REST framework, I tried using different views and class based views solving nothing.

Any hint or suggestion is really appreciated thanks.

# models.py

class Hardware(models.Model):
    name = models.CharField(max_length=25)
    category = models.CharField(choices=CATEGORY_CHOICES, max_length=2)

    def get_api_url(self):
        return api_reverse("category-api-postings:post-rud", kwargs={'category': self.category})

#views.py

class HardwareListView(generics.ListCreateAPIView):
    pass
    lookup_field = 'pk'
    serializer_class = HardwareSerializer

    def get_queryset(self):
        query = self.request.GET.get("q")
        qs = Hardware.objects.all()
        if query is not None:
            qs = qs.filter(Q(title__icontains=query) | Q(content__icontains=query)).distinct()
        return qs


class HardwareRudView(generics.RetrieveUpdateDestroyAPIView):
    pass
    lookup_field = 'category'
    serializer_class = HardwareSerializer

    def get_queryset(self):
        return Hardware.objects.all()

#urls.py

app_name = 'category-api-postings'

urlpatterns = [
    path('', exercise_view),
    path('list-api/', HardwareListView.as_view(), name='all'),
    path('list-api/<str:category>/', HardwareRudView.as_view(), name='post-rud')

#serializer.py

class HardwareSerializer(serializers.ModelSerializer):

    url = serializers.SerializerMethodField(read_only=True)

    class Meta:
        model = Hardware
        fields = [
            'url',
            'pk',
            'name',
            'category'
        ]
    read_only_fields = ['user']

    def get_url(self, obj):
        return obj.get_api_url()

@EugenePrikazchikov Sorry for late response: dpaste.com/2GX88FA — JLeno46
– JLeno46, Commented Sep 30, 2019 at 12:16

Eugene Prikazchikov · Accepted Answer · 2019-09-30 13:19:41Z

1

As I understand, you want url /list-api/HD/ to return all Hardware objects from given category. For that HardwareRudView must inherit ListAPIView, not RetrieveUpdateDestroyAPIView. For example, like this:

class HardwareRudView(generics.ListAPIView):
    serializer_class = HardwareSerializer

    def get_queryset(self):
        category = self.kwargs['category']
        return Hardware.objects.filter(category=category)

See related docs: https://www.django-rest-framework.org/api-guide/filtering/#filtering-against-the-url

answered Sep 30, 2019 at 13:19

Eugene Prikazchikov

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1 Comment

JLeno46 Over a year ago

I swear I red this one second after I've done the same thing, it works perfectly, thanks for your time

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