10 KiB
ViewSets
After routing has determined which controller to use for a request, your controller is responsible for making sense of the request and producing the appropriate output.
Django REST framework allows you to combine the logic for a set of related views in a single class, called a ViewSet. In other frameworks you may also find conceptually similar implementations named something like 'Resources' or 'Controllers'.
A ViewSet class is simply a type of class-based View, that does not provide any method handlers such as .get() or .post(), and instead provides actions such as .list() and .create().
The method handlers for a ViewSet are only bound to the corresponding actions at the point of finalizing the view, using the .as_view() method.
Typically, rather than explicitly registering the views in a viewset in the urlconf, you'll register the viewset with a router class, that automatically determines the urlconf for you.
Example
Let's define a simple viewset that can be used to list or retrieve all the users in the system.
from django.contrib.auth.models import User
from django.shortcuts import get_object_or_404
from myapps.serializers import UserSerializer
from rest_framework import viewsets
from rest_framework.response import Response
class UserViewSet(viewsets.ViewSet):
"""
A simple ViewSet that for listing or retrieving users.
"""
def list(self, request):
queryset = User.objects.all()
serializer = UserSerializer(queryset, many=True)
return Response(serializer.data)
def retrieve(self, request, pk=None):
queryset = User.objects.all()
user = get_object_or_404(queryset, pk=pk)
serializer = UserSerializer(user)
return Response(serializer.data)
If we need to, we can bind this viewset into two separate views, like so:
user_list = UserViewSet.as_view({'get': 'list'})
user_detail = UserViewSet.as_view({'get': 'retrieve'})
Typically we wouldn't do this, but would instead register the viewset with a router, and allow the urlconf to be automatically generated.
from myapp.views import UserViewSet
from rest_framework.routers import DefaultRouter
router = DefaultRouter()
router.register(r'users', UserViewSet)
urlpatterns = router.urls
Rather than writing your own viewsets, you'll often want to use the existing base classes that provide a default set of behavior. For example:
class UserViewSet(viewsets.ModelViewSet):
"""
A viewset for viewing and editing user instances.
"""
serializer_class = UserSerializer
queryset = User.objects.all()
There are two main advantages of using a ViewSet class over using a View class.
- Repeated logic can be combined into a single class. In the above example, we only need to specify the
querysetonce, and it'll be used across multiple views. - By using routers, we no longer need to deal with wiring up the URL conf ourselves.
Both of these come with a trade-off. Using regular views and URL confs is more explicit and gives you more control. ViewSets are helpful if you want to get up and running quickly, or when you have a large API and you want to enforce a consistent URL configuration throughout.
Marking extra actions for routing
The default routers included with REST framework will provide routes for a standard set of create/retrieve/update/destroy style operations, as shown below:
class UserViewSet(viewsets.ViewSet):
"""
Example empty viewset demonstrating the standard
actions that will be handled by a router class.
If you're using format suffixes, make sure to also include
the `format=None` keyword argument for each action.
"""
def list(self, request):
pass
def create(self, request):
pass
def retrieve(self, request, pk=None):
pass
def update(self, request, pk=None):
pass
def partial_update(self, request, pk=None):
pass
def destroy(self, request, pk=None):
pass
If you have ad-hoc methods that you need to be routed to, you can mark them as requiring routing using the @detail_route or @list_route decorators.
The @detail_route decorator contains pk in its URL pattern and is intended for methods which require a single instance. The @list_route decorator is intended for methods which operate on a list of objects.
For example:
from django.contrib.auth.models import User
from rest_framework import status
from rest_framework import viewsets
from rest_framework.decorators import detail_route, list_route
from rest_framework.response import Response
from myapp.serializers import UserSerializer, PasswordSerializer
class UserViewSet(viewsets.ModelViewSet):
"""
A viewset that provides the standard actions
"""
queryset = User.objects.all()
serializer_class = UserSerializer
@detail_route(methods=['post'])
def set_password(self, request, pk=None):
user = self.get_object()
serializer = PasswordSerializer(data=request.DATA)
if serializer.is_valid():
user.set_password(serializer.data['password'])
user.save()
return Response({'status': 'password set'})
else:
return Response(serializer.errors,
status=status.HTTP_400_BAD_REQUEST)
@list_route()
def recent_users(self, request):
recent_users = User.objects.all().order('-last_login')
page = self.paginate_queryset(recent_users)
serializer = self.get_pagination_serializer(page)
return Response(serializer.data)
The decorators can additionally take extra arguments that will be set for the routed view only. For example...
@detail_route(methods=['post'], permission_classes=[IsAdminOrIsSelf])
def set_password(self, request, pk=None):
...
The @action decorator will route POST requests by default, but may also accept other HTTP methods, by using the methods argument. For example:
@detail_route(methods=['post', 'delete'])
def unset_password(self, request, pk=None):
...
The two new actions will then be available at the urls ^users/{pk}/set_password/$ and ^users/{pk}/unset_password/$
API Reference
ViewSet
The ViewSet class inherits from APIView. You can use any of the standard attributes such as permission_classes, authentication_classes in order to control the API policy on the viewset.
The ViewSet class does not provide any implementations of actions. In order to use a ViewSet class you'll override the class and define the action implementations explicitly.
GenericViewSet
The GenericViewSet class inherits from GenericAPIView, and provides the default set of get_object, get_queryset methods and other generic view base behavior, but does not include any actions by default.
In order to use a GenericViewSet class you'll override the class and either mixin the required mixin classes, or define the action implementations explicitly.
ModelViewSet
The ModelViewSet class inherits from GenericAPIView and includes implementations for various actions, by mixing in the behavior of the various mixin classes.
The actions provided by the ModelViewSet class are .list(), .retrieve(), .create(), .update(), and .destroy().
Example
Because ModelViewSet extends GenericAPIView, you'll normally need to provide at least the queryset and serializer_class attributes, or the model attribute shortcut. For example:
class AccountViewSet(viewsets.ModelViewSet):
"""
A simple ViewSet for viewing and editing accounts.
"""
queryset = Account.objects.all()
serializer_class = AccountSerializer
permission_classes = [IsAccountAdminOrReadOnly]
Note that you can use any of the standard attributes or method overrides provided by GenericAPIView. For example, to use a ViewSet that dynamically determines the queryset it should operate on, you might do something like this:
class AccountViewSet(viewsets.ModelViewSet):
"""
A simple ViewSet for viewing and editing the accounts
associated with the user.
"""
serializer_class = AccountSerializer
permission_classes = [IsAccountAdminOrReadOnly]
def get_queryset(self):
return self.request.user.accounts.all()
Also note that although this class provides the complete set of create/list/retrieve/update/destroy actions by default, you can restrict the available operations by using the standard permission classes.
ReadOnlyModelViewSet
The ReadOnlyModelViewSet class also inherits from GenericAPIView. As with ModelViewSet it also includes implementations for various actions, but unlike ModelViewSet only provides the 'read-only' actions, .list() and .retrieve().
Example
As with ModelViewSet, you'll normally need to provide at least the queryset and serializer_class attributes. For example:
class AccountViewSet(viewsets.ReadOnlyModelViewSet):
"""
A simple ViewSet for viewing accounts.
"""
queryset = Account.objects.all()
serializer_class = AccountSerializer
Again, as with ModelViewSet, you can use any of the standard attributes and method overrides available to GenericAPIView.
Custom ViewSet base classes
You may need to provide custom ViewSet classes that do not have the full set of ModelViewSet actions, or that customize the behavior in some other way.
Example
To create a base viewset class that provides create, list and retrieve operations, inherit from GenericViewSet, and mixin the required actions:
class CreateListRetrieveViewSet(mixins.CreateModelMixin,
mixins.ListModelMixin,
mixins.RetrieveModelMixin,
viewsets.GenericViewSet):
"""
A viewset that provides `retrieve`, `create`, and `list` actions.
To use it, override the class and set the `.queryset` and
`.serializer_class` attributes.
"""
pass
By creating your own base ViewSet classes, you can provide common behavior that can be reused in multiple viewsets across your API.