python - DRF doesn't update instead create new instance in modelserializer

Question

Searched throughout SO to find the matching questions doesn't answer mine as there are only few explanations. So hoping to get an answer here.

I have a model named "testcase" with pk set as "testcase_name". On update operation in the serializer, instead of updating a new instance is created everytime. I suspect it is because of the pk.

serializer.py

class TestcaseSerializer(serializers.ModelSerializer):
    class Meta:
        model = testcase
        lookup_field = 'testcase_name'
        fields = ("testcase_name", 'description')

    def update(self, instance, validated_data):
        print(instance)  # returns test2 instead it should be test1 which is the current instance

        # ret = super(TestcaseSerializer, self).update(instance, validated_data)
        [setattr(instance, key, value)
         for key, value in validated_data.items()]
        instance.save() 
        print(instance)# returns test2 
        return instance

models.py

class testcase(models.Model):
    testcase_name = models.CharField(
        max_length=20, primary_key=True)
    description = models.CharField(max_length=100, blank=True)

    def __str__(self):
        return self.testcase_name

views.py

class Testcaseviewset(viewsets.ModelViewSet):
    queryset = testcase.objects.all()
    serializer_class = TestcaseSerializer
    lookup_field = 'testcase_name'

Is there any way to solve this in the serializer itself not from the views.

question from:https://stackoverflow.com/questions/65875702/drf-doesnt-update-instead-create-new-instance-in-modelserializer

Answer 1

Waitting for answers