Cannot resolve keyword 'author' into field - django

Question

Here is the issue.I am trying to delete the tags related to my model. I can create them but whenever i try to use HTTP DELETE on ExampleModelTags, i face with the following issue.
Error: Cannot resolve keyword 'author' into field. Choices are: id, examplemodel, examplemodel_id, tag, timestamp
I can't understand what is the issue, i can create them so the algorithm works. The tags can connect to their parent model . But whenever i try to do HTTP DELETE on ExampleModelTags, i get that issue. Where is the problem that i don't see?
Model.py
class ExampleModelTag(models.Model):
id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
tag = models.CharField(max_length=35,null=True,blank=True)
examplemodel = models.ForeignKey(ExampleModel, on_delete=models.CASCADE,null=True,blank=True, related_name='examplemodeltags')
timestamp = models.DateTimeField(auto_now_add=True)
class ExampleModel(models.Model):
id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
author = models.ForeignKey(User, on_delete=models.CASCADE,null=True,related_name='examplemodels')
examplemodel = models.CharField(unique=False,max_length=100,null=True,blank=True)
timestamp = models.DateTimeField(unique=False,auto_now_add=True)
Serializer.py
class ExampleModelTagSerializer(serializers.ModelSerializer):
class Meta:
model = ExampleModelTag
fields = ("id","examplemodel","tag","timestamp")
def validate(self, attrs):
attrs = super().validate(attrs)
if attrs['examplemodel'].author.id != self.context['request'].user.pk:
raise ValidationError('Unauthorized Request')
return attrs
class ExampleModelSerializer(serializers.ModelSerializer):
examplemodeltags_set = ExampleModelTagSerializer(source='examplemodeltags',required=False,many=True)
class Meta:
model = ExampleModel
fields = ("id","author","examplemodel","examplemodeltags_set","timestamp")
def validate(self, attrs):
attrs = super().validate(attrs)
if attrs['author'].id != self.context['request'].user.pk:
raise ValidationError('Unauthorized Request')
return attrs
Views.py
class ExampleModelViewSet(viewsets.ModelViewSet):
permission_classes = (IsAuthenticated,)
queryset = ExampleModel.objects.all().order_by('-timestamp')
serializer_class = ExampleModelSerializer
filter_backends = [UserFilterBackend]
class ExampleModelTagViewSet(viewsets.ModelViewSet):
permission_classes = (IsAuthenticated,)
queryset = ExampleModelTag.objects.all()
serializer_class = ExampleModelTagSerializer
filter_backends = [UserFilterBackend]
Filters.py
class UserFilterBackend(filters.BaseFilterBackend):
def filter_queryset(self, request, queryset, view):
return queryset.filter(
author=request.user
)

Answer 1

You can not use the UserFilterBackend on the ExampleModelTagViewSet, since an ExampleModelTag has no author field. You thus should rewrite the ExampleModelTagViewSet to:
class ExampleModelTagViewSet(viewsets.ModelViewSet):
# ⋮
filter_backends = [] # ← UserFilterBackend not applicable
If you want to fetch ExampleModelTags for which an ExampleModel exists that links to that ExampleModelTag record, and has as author the logged in user, you can specify this with:
class ExampleModelAuthorBackend(filters.BaseFilterBackend):
def filter_queryset(self, request, queryset, view):
return queryset.filter(
examplemodel__author=request.user
)
and then use that one to filter the ExampleModelTags:
class ExampleModelTagViewSet(viewsets.ModelViewSet):
# ⋮
filter_backends = [ExampleModelAuthorBackend]

Answer 2

class UserFilterBackend(filters.BaseFilterBackend):
def filter_queryset(self, request, queryset, view):
return queryset.filter(
examplemodel__author=request.user
)