How can I add additional top level JSON fields using the ModelSerializer

Question

I am using the ModelSerializer from the Django Rest Framework to create an API. The ModelSerializer works great for returning JSON lists of whatever I query the database for. But I need to have some additional fields at the root level of the JSON response. How can I bump the query result to another level and add custom fields at the root of the JSON object?

This is what the API query returns:

HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Content-Type: application/json
Vary: Accept

[
    {
        "user": {
            "username": "myuser"
        },
        "content": "Another tweet",
        "timesince": "2 weeks, 3 days",
        "url": "/tweet/3/",
        "id": 3
    },
    {
        "user": {
            "username": "myuser"
        },
        "content": "a tweet",
        "timesince": "2 weeks, 3 days",
        "url": "/tweet/2/",
        "id": 2
    }
]

This is what I want:

HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Content-Type: application/json
Vary: Accept

{
    "custom_field": "custom value",
    "result": [
            {
                "user": {
                    "username": "myuser"
                },
                "content": "Another tweet",
                "timesince": "2 weeks, 3 days",
                "url": "/tweet/3/",
                "id": 3
            },
            {
                "user": {
                    "username": "myuser"
                },
                "content": "a tweet",
                "timesince": "2 weeks, 3 days",
                "url": "/tweet/2/",
                "id": 2
            }
    ]
}

serializer.py:

from django.utils.timesince import timesince

from rest_framework import serializers

from tweets.models import Tweet
from accounts.api.serializers import UserDisplaySerializer

class TweetSerializer(serializers.ModelSerializer):
    user = UserDisplaySerializer(read_only=True)
    timesince = serializers.SerializerMethodField()
    url = serializers.CharField(source='get_absolute_url', read_only=True)

    class Meta:
        model = Tweet
        fields = [
            'user',
            'content',
            'timesince',
            'url',
            'id',
            ]

    def get_timesince(self, obj):
        return timesince(obj.created)

views.py:

from django.db.models import Q
from rest_framework import generics
from rest_framework import exceptions
from rest_framework import permissions

from tweets.models import Tweet
from tweets.api import serializers

class TweetListAPIView(generics.ListAPIView):
    serializer_class = serializers.TweetSerializer

    def get_queryset(self, *args, **kwargs):
        queryset = Tweet.objects.all()
        queryset = queryset.order_by('-id')

        return queryset

Peter Sobhi · Accepted Answer · 2018-02-21 20:32:23Z

3

You can do this by overriding the list method of the ListAPIView and then adding this new field to the response:

from rest_framework.response import Response

def list(self, request, *args, **kwargs):
    queryset = self.get_queryset()
    serializer = self.get_serializer(queryset, many=True)

    response_data = {'custom_field': 'custom value',
                     'result': serializer.data}

    return Response(response_data)

edited Feb 21, 2018 at 20:32

answered Feb 21, 2018 at 20:16

Peter Sobhi

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4 Comments

ni9e Over a year ago

Yes, that works. Had to import rest_framework.response.Response

Peter Sobhi Over a year ago

Yes.. Edited :)

SirSaleh Over a year ago

works like a charm! thank you. To make the order of fields fixed, just use OrderedDict from collections library.

Marko Benko Over a year ago

Also, check this answer if you need to apply filters and pagination to queryset.

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