How to implement a hierarchy of resources (eg. /parents/<id>/children) in Django REST Framework

Question

I couldn't find any information on how to achieve this in the tutorial at the Django REST Framework website and I haven't managed to find it in the documentation, though I'm sure it's there somewhere.

I want issues to be the parent resource and pages to be the children so that /issues/1/pages returns all pages with issue_id of 1.

Is there a good way to achieve this using generic class based views?

Here's what I have so far.

restAPI/urls.py:

from django.conf.urls import patterns, url
from rest_framework.urlpatterns import format_suffix_patterns
from restAPI import views

urlpatterns = patterns('',
    url(r'^issues/$', views.IssueList.as_view()),
    url(r'^issues/(?P<pk>[0-9]+)/$', views.IssueDetail.as_view()),


    url(r'^issues/(?P<issue_id>[0-9]+)/pages/$', views.PageList.as_view()),    
    url(r'^pages/(?P<pk>[0-9]+)/$', views.PageDetail.as_view()),
)

urlpatterns = format_suffix_patterns(urlpatterns)

restAPI/models.py:

from django.db import models

class Issue(models.Model):
    created = models.DateTimeField(auto_now_add=True)
    revision = models.IntegerField(default = 1)
    issue_date = models.DateTimeField(auto_now_add=True)
    issue_image_url = models.CharField(max_length=100)

class Page(models.Model):
    created = models.DateTimeField(auto_now_add=True)
    page_number = models.IntegerField()
    standard_page_url = models.CharField(max_length=100, default='')
    large_page_url = models.CharField(max_length=100, default='')
    thumbnail_url = models.CharField(max_length=100, default='')

    issue = models.ForeignKey(Issue, related_name="pages")

    class Meta:
        ordering = ('page_number',)

restAPI/serializers.py:

from rest_framework import serializers
from restAPI.models import Page, Issue

class IssueSerializer(serializers.ModelSerializer):
    class Meta:
        model = Issue
        fields = ('id', 'created', 'revision', 'issue_date', 'issue_image_url')

class PageSerializer(serializers.ModelSerializer):       
    class Meta:
        model = Page
        fields = ('id', 'created', 'page_number', 'standard_page_url', 'large_page_url', 'thumbnail_url')

restAPI/views.py:

from restAPI.models import Page, Issue
from restAPI.serializers import PageSerializer, IssueSerializer
from rest_framework import mixins
from rest_framework import generics

class IssueList(mixins.ListModelMixin,
                  mixins.CreateModelMixin,
                  generics.GenericAPIView):
    queryset = Issue.objects.all()
    serializer_class = IssueSerializer

    def get(self, request, *args, **kwargs):
        return self.list(request, *args, **kwargs)

    def post(self, request, *args, **kwargs):
        return self.create(request, *args, **kwargs)

class IssueDetail(mixins.RetrieveModelMixin,
                    mixins.UpdateModelMixin,
                    mixins.DestroyModelMixin,
                    generics.GenericAPIView):
    queryset = Issue.objects.all()
    serializer_class = IssueSerializer

    def get(self, request, *args, **kwargs):
        return self.retrieve(request, *args, **kwargs)

    def put(self, request, *args, **kwargs):
        return self.update(request, *args, **kwargs)

    def delete(self, request, *args, **kwargs):
        return self.destroy(request, *args, **kwargs)  

class PageList(mixins.ListModelMixin,
                  mixins.CreateModelMixin,
                  generics.GenericAPIView):
    queryset = Page.objects.all()
    serializer_class = PageSerializer

    def get(self, request, *args, **kwargs):
        print kwargs
        return self.list(request, *args, **kwargs)

    def post(self, request, *args, **kwargs):
        return self.create(request, *args, **kwargs)

class PageDetail(mixins.RetrieveModelMixin,
                   mixins.UpdateModelMixin,
                   mixins.DestroyModelMixin,
                   generics.GenericAPIView):
    queryset = Page.objects.all()
    serializer_class = PageSerializer

    def get(self, request, *args, **kwargs):
        return self.retrieve(request, *args, **kwargs)

    def put(self, request, *args, **kwargs):
        return self.update(request, *args, **kwargs)

    def delete(self, request, *args, **kwargs):
        return self.destroy(request, *args, **kwargs)

How can I implement this sort of relationship between issues and pages?

Answer 1

I added def get_queryset(self): issue_id = self.kwargs['issue_id'] return Page.objects.filter(issue_id = issue_id) to PageList and now GET works for issue/ /pages. Now I just have to figure out how to post as well.

I added def pre_save(self, obj): obj.issue_id = self.kwargs['issue_id'] to PageList and now POST works too. Querying pages from an issue that doesn't exist returns an empty result rather than 404 not found though. If anyone knows of a better way to do this I'm very interested to hear about it.

If your method get_queryset(self) returns an empty list instead of 404 NOT FOUND, I would suggest to use the shortcut function get_list_or_404 from django. The method could look like this:

from django.shortcuts import get_list_or_404

def get_queryset(self):
    filter = {}
    filter['issue_id'] = self.kwargs['issue_id']
    return get_list_or_404(self.queryset, **filter)

I know this is an old post, but maybe this could help other people having the same or some similar problem.

Answer 2

Here is another way I've done this:

views.py

from models import Customer, Order
from serializers import CustomerSerializer, OrderSerializer

from rest_framework import generics

class CustomerList(generics.ListCreateAPIView):
    queryset = Customer.objects.all()
    serializer_class = CustomerSerializer

class CustomerDetail(generics.RetrieveUpdateDestroyAPIView)
    queryset = Customer.objects.all()
    serializer_class = CustomerSerializer

class OrdersByCustomer(generics.ListCreateAPIView):
    queryset = Order.objects.all()
    serializer_class = OrderSerializer

    def get_queryset(self):
        customer_pk = self.kwargs['customer_pk']
        return self.queryset.filter(customer__pk=customer_pk)

    def pre_save(self, obj):
        obj.customer_id = self.kwargs['customer_pk'] 

class OrderDetail(generics.RetrieveUpdateDestroyAPIView):
    queryset = Order.objects.all()
    serializer_class = OrderSerializer

serializers.py

from models import Customer, Order

from rest_framework import serializers
from rest_framework.reverse import reverse

class OrderSerializer(serializers.HyperlinkedModelSerializer)

    class Meta:
        model = Order

class CustomerSerializer(serializers.HyperlinkedModelSerializer)

    orders = serializers.SerializerMethodField('get_customer_orders')

    def get_customer_orders(self, obj):
        return reverse('ordersbycustomer-list', 
               args=[obj.pk], request=self.context['request'])

    class Meta:
        model = Customer

urls.py

from django.conf.urls import patterns, include, url
from views import OrdersByCustomer, CustomerDetail, CustomerList

urlpatterns = patterns("",
    url(r'^customers/(?P<customer_pk>.+)/orders/$', OrdersByCustomer.as_view(), name='ordersbycustomer-list'),
    url(r'^customers/(?P<pk>.+)/$', CustomerDetail.as_view(), name='customer-detail'),
    url(r'^customers/$', CustomerList.as_view(), name='customer-list'),
    )

There is more code involved than with Viewsets/Routers but this gives you much more control over what is going on.

Here I have chosen to only expose orders as children of a customer. Since they are separated, you can use different serializer classes for list vs detail.

Answer 3

Here is how I have achieved this using the new ViewSets and Routers from Rest-Framework version 2.3:

views.py:

from rest_framework import viewsets
from rest_framework.response import Response
from models import Order, OrderLine
from serializers import OrderSerializer, OrderLineSerializer

class OrderViewSet(viewsets.ModelViewSet):
    queryset = Order.objects.all()
    serializer_class = OrderSerializer

    @link()
    def lines(self, request, pk=None):
        queryset = OrderLine.objects.filter(order__pk=pk)
        serializer = OrderLineSerializer(queryset,
                           context={'request':request},
                           many=True)
        return Response(serializer.data)

class OrderLineViewSet(viewsets.ModelViewSet):
    queryset = OrderLine.objects.all()
    serializer_class = OrderLineSerializer

serializers.py

from rest_framework import serializers
from models import Order, OrderLine

class OrderSerializer(serializers.HyperlinkedModelSerializer):
    lines = serializers.HyperlinkedIdentityField(view_name='order-lines')

    class Meta:
        model = Order


class OrderLineSerializer(serializers.HyperlinkedModelSerializer):

    class Meta:
        model = OrderLine

urls.py

from views import OrderViewSet, OrderLineViewSet
from rest_framework.routers import DefaultRouter

router = DefaultRouter()
router.register(r'order', OrderViewSet)
router.register(r'orderline', OrderLineViewSet)
urlpatterns = router.urls

Now 'order/id/lines' will return a list of serialized Order Lines that have a relationship with the Order identified by that id.

Any method on a ViewSet decorated with @link or @action will be given a URL when you register the view with the router.