CODEWITHSUNDEEP
djangodjango-rest-framework
chadgh
chadgh

Reputation: 9753

DRF: custom ordering on related serializers

I've got two serializers one for an Instructor and one for a Course. The Instructor serializer has a defined relationship to the courses like so:

courses = CourseSerializer(many=True, read_only=True)

How do I specify an order to the courses in the instructor serializer?

Note: I have defined the ordering value in the Course Meta class, but it is the default sorting I want everywhere else. What I want is a custom ordering for api output (specifically dept, number, -semester rather than the default -semester).

Upvotes: 20

Views: 14897

Answers (4)

TheAxeR
TheAxeR

Reputation: 622

Since it is read only, wouldn't it be just as easy to use a serializer method for that field?

class InstructorSerializer(serializers.ModelSerializer):
    courses = serializers.SerializerMethodField()

    def get_courses(self, obj):
         ordered_queryset = <do your magic here>
         return CourseSerializer(ordered_queryset, many=True, context=self.context).data

Upvotes: 30

Endre Both
Endre Both

Reputation: 5730

Since Django 1.7, you can specify a queryset for prefetch_related. Using prefetch incurs just one additional database query instead of one per parent object with SerializerMethodField.

from rest_framework import viewsets
from django.db.models import Prefetch

class InstructorViewSet(viewsets.ModelViewSet):
    queryset = Instructor.objects.prefetch_related(Prefetch(
        'courses',
        queryset=Course.objects.order_by('dept', 'number')))

Upvotes: 12

Kobold
Kobold

Reputation: 1747

This should be doable simply by providing an ordered queryset argument to your field declaration:

class InstructorSerializer(serializers.ModelSerializer):
    courses = CourseSerializer(
        queryset=Course.objects.order_by('...'),
        many=True,
        read_only=True,
    )

Further details: http://www.django-rest-framework.org/api-guide/relations/#the-queryset-argument

Upvotes: -3

Roba
Roba

Reputation: 688

In this case you should modulate the ordering via the viewset queryset. I would imagine the following:

queryset = Instructor.objects.select_related('courses').order_by('courses__number')

Upvotes: 0

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