Nested create ignore to_internal_value method

[Amoki]

I need to abstract a nested representation:

// The request body I need
{
   "name": "the name",
   "topic_type": "the type"
}

instead of

{
    "name": "the name",
    "topic_type": {
        "topic_type": "the type"
    }
}

To achieve that, I use these serializers and models :

class TopicType(models.Model):
    topic_type = models.CharField(max_length=64)


class Topic(models.Model):
    name = models.CharField(max_length=64)
    topic_type = models.ForeignKey('TopicType', on_delete=models.CASCADE)



class TopicTypeSerializer(serializers.ModelSerializer):
    class Meta:
        model = TopicType
        fields = ('topic_type',)

    def to_representation(self, instance):
        return instance.topic_type

    def to_internal_value(self, data):
        return {'topic_type': data}

    def create(self, validated_data):
        return TopicType.objects.get_or_create(**validated_data)[0]


class TopicSerializer(WritableNestedModelSerializer):
    topic_type = TopicTypeSerializer()

    class Meta:
        model = Topic
        fields = ('name', 'topic_type')

On the line https://github.com/beda-software/drf-writable-nested/blob/master/drf_writable_nested/mixins.py#L174, it uses the initial_data and not the validated_data (so it doesn't use the to_internal_value's return) and crash with

File ".../lib/python3.6/site-packages/drf_writable_nested/mixins.py", line 108, in _get_related_pk
    pk = data.get('pk') or data.get(model_class._meta.pk.attname)
AttributeError: 'str' object has no attribute 'get'

My issue seems similar to https://github.com/beda-software/drf-writable-nested/issues/39 It would be nice to be able to customize nested deserialization behavior!

[ruscoder]

Hello @Amoki! It is impossible to do it now because we always use initial_data instead of validated_data. Follow #57, maybe it will add some flexibility in the near future.

[j-bernard]

Hi @ruscoder. I don't see the reason why you use initial_data at that point as the data that will effectively be used in the object is validated_data. Could you please give more details? With the current implementation, what would be the best way to handle this kind of nested representation?