Django Rest Framework - Append JSON to Model Serialization

Question

I have a model is pretty straight forward and I've created a property on the model to essentially return child data as JSON. The property is simple:

@property
def question_data(self):
    from api.models import TemplateQuestion
    questions = TemplateQuestion.objects.filter(template__id=self.template.id)
    question_dict = [obj.as_dict() for obj in questions]
    return(json.dumps(question_dict, separators=(',', ': ')))

Which does its job and outputs valid JSON. That said I'm at a total loss of how to add that property to the Serializer as JSON and not a string like

{
    "questions": "[{\"sequence\": 2,\"next_question\": \"\",\"modified_at\": \"2016-01-27T19:59:07.531872+00:00\",\"id\": \"7b64784e-a41d-4019-ba6e-ed8b31f99480\",\"validators\": []},{\"sequence\": 1,\"next_question\": null,\"modified_at\": \"2016-01-27T19:58:56.587856+00:00\",\"id\": \"99841d91-c459-45ff-9f92-4f75c904fe1e\",\"validators\": []}]"
}

It's stringifying the JSON and which I need as proper JSON.

Serializer is probably too basic but I haven't worked with DRF in a while and have never tried to append JSON to the serialized output.

class BaseSerializer(serializers.ModelSerializer):

    class Meta:
        abstract = True

class SurveySerializer(BaseSerializer):
        included_serializers = {
            'landing_page': 'api.serializers.LandingPageSerializer',
            'trigger': 'api.serializers.TriggerSerializer',
            'template': 'api.serializers.TemplateSerializer'
        }

        questions = serializers.ReadOnlyField(source='question_data')

        class Meta:
            model = Survey
            fields = ('id',
                      'name',
                      'slug',
                      'template',
                      'landing_page',
                      'trigger',
                      'trigger_active',
                      'start_date',
                      'end_date',
                      'description',
                      'fatigue_limit',
                      'url',
                      'questions',)
            meta_fields = ('created_at', 'modified_at')

I'll add that I'm also bolting on the Django Rest Framework JSON API formatting but I think that in the end I'm just not getting how to append JSON to a model's serialization without it being returned as a string.

this help? Can you call it a JSONField? stackoverflow.com/questions/22434869/… — mreppy
– mreppy, Commented Jan 28, 2016 at 18:10
This is leading me down the path of just adding a JSONField to the model that will be set as needed and then that'll just pull through in the model serialization. Makes sense and I'm going to do that to get unstuck, but I would still like to understand appending JSON as needed as it'll be a very handy/needed output. — bryan
– bryan, Commented Jan 28, 2016 at 18:23

Daniel Roseman · Accepted Answer · 2016-01-28 19:19:18Z

2

You should not be dumping the results of the method to JSON. Just return the dict; DRF's serializer will take care of converting it.

answered Jan 28, 2016 at 19:19

Daniel Roseman

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2 Comments

mreppy Over a year ago

Thanks, I might be needing this in the near future!

bryan Over a year ago

Removing the JSON dump was correct and now there's no need to infecting related models with JSONField properties. Cheers.

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