Django-rest-framework, nested objects in Serializers

Question

I would like to have a nested object inside a serializer instead of just the foreignkey (or url). As this documentation says, I just had to specify the serializer class of the nested object in the parent serializer:

# Models

class NestedSample(models.Model):
    something = models.CharField(max_length=255)

class Sample(models.Model):
    thing = models.BooleanField()
    nested = models.ForeignKey(NestedSample)

# Serializers

class NestedSampleSerializer(serializers.HyperlinkedModelSerializer):

    class Meta:
        model = api_models.NestedSample

class SampleSerializer(serializers.HyperlinkedModelSerializer):
    nested = NestedSampleSerializer() # HERE!

    class Meta:
        model = api_models.Sample

# Views

class NestedSampleViewSet(viewsets.ModelViewSet):
    queryset = api_models.NestedSample.objects.all()
    serializer_class = api_serializers.NestedSampleSerializer

class SampleViewSet(viewsets.ModelViewSet):
    queryset = api_models.Sample.objects.all()
    serializer_class = api_serializers.SampleSerializer

This works very well when I get the objects, but it is not possible to create (=POST) Sample objects anymore, I get the error:

{u'non_field_errors': [u'Invalid data']}

I tried to overwrite the create method in the viewset to get the object using the pk:

class SampleViewSet(viewsets.ModelViewSet):
    queryset = api_models.Sample.objects.all()
    serializer_class = api_serializers.SampleSerializer

    def create(self, request):
        request.DATA['nested'] = get_object_or_404(api_models.NestedSample, pk=request.DATA['nested'])
        return super(SampleViewSet, self).create(request)

But it doesn't work as well.

Any idea?

I also found this question I can relate with which of course solves the problem but do not let me expose the full nested object, so back to the beginning.

Thanks,

Answer 1

I can think of two solutions to this problem. I prefer the first one.

First solution:

Use a django model form to create objects. Override the create and update methods. A sample create method:

def create(self, request):
    form = SampleForm(data=request.POST)
    if form.is_valid():
        instance = form.save(commit=False)
        instance.save()
        return Response(dict(id=instance.pk), status=status.HTTP_201_CREATED)
    return Response(form.errors, status=status.HTTP_400_BAD_REQUEST)

this way you can create Sample objects with any kind of validation you like.

Second solution:

Override get_serializer_class method and return serializer class based on request method. Define two serializers one for post and put and one for list and retrieve.