How to add a serializer field in DRF for GET only not POST?

Question

I am working on an existing DRF codebase and want to add a last_build field to return on a GET request only. I do NOT want this to affect anything to do with POST requests. I have created a method that returns the field I am looking for and have successfully tested that it returns the data I want, however I have not yet tested if this will affect existing POST requests.

class JobSerializer(serializers.ModelSerializer):
    name = serializers.CharField(required=True, max_length=150)
    product = ProductSerializer(many=False, required=True)
    platform = PlatformSerializer(many=False, required=True)
    stages = StageSerializer(many=True, required=False)
    last_build = serializers.SerializerMethodField()

    def get_last_build(self, name):
        latest_build = JobExecution.manager.filter(job__name=name.name)
        return latest_build.last().build_id

    class Meta:
        model = Job
        fields = ("name", "product", "platform", "stages", "last_build")
        validators = [
            UniqueTogetherValidator(
                queryset=Job.manager.all(), fields=("name", "platform", "product")
            )
        ]

    def create(self, validated_data):
        # Create objects from data
        try:
            product_data = validated_data.pop("product", None)
            if product_data:
                ps = ProductSerializer()
                validated_data["product"] = ps.create(product_data)
            else:
                logger.exception("product is not valid")

            platform_data = validated_data.pop("platform", None)
            if platform_data:
                ps = PlatformSerializer()
                validated_data["platform"] = ps.create(platform_data)
            else:
                logger.exception("platform is not valid")

            stage_data = validated_data.pop("stages", [])
            stages = []

            the_job = Job.manager.get_or_create(**validated_data)[0]
            if stage_data:
                for stage_data in stage_data:
                    ss = StageSerializer()
                    stage_data["job"] = the_job
                    the_stage = ss.create(stage_data)
            return the_job
        except Exception as e:
            logger.exception(e)
            raise e

Here is a snippet of the api view for post:

class JobView(GenericAPIView):
    def post(self, request, format=None):
        serializer = JobSerializer(data=request.data)
        logger.debug(request.data)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data, status=status.HTTP_201_CREATED)
        else:
            logger.info("POST request for Job failed: %s", serializer.errors)
            return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

Answer 1

You can add some fields for serializer method filed for skip on POST/PUT/PATCH requests. Add required=False for skip checking data, and read_only=True for skip POST request.

Example:

class JobSerializer(serializers.ModelSerializer):
    name = serializers.CharField(required=True, max_length=150)
    product = ProductSerializer(many=False, required=True)
    platform = PlatformSerializer(many=False, required=True)
    stages = StageSerializer(many=True, required=False)
    last_build = serializers.SerializerMethodField(required=False, read_only=True)