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213 lines
8.9 KiB
Markdown
213 lines
8.9 KiB
Markdown
<a class="github" href="viewsets.py"></a>
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# ViewSets
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> 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.
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>
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> — [Ruby on Rails Documentation][cite]
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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'.
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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()`.
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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.
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Typically, rather than exlicitly 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.
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## Example
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Let's define a simple viewset that can be used to listing or retrieving all the users in the system.
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class UserViewSet(viewsets.ViewSet):
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"""
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A simple ViewSet that for listing or retrieving users.
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"""
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def list(self, request):
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queryset = User.objects.all()
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serializer = UserSerializer(queryset, many=True)
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return Response(serializer.data)
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def retrieve(self, request, pk=None):
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queryset = User.objects.all()
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user = get_object_or_404(queryset, pk=pk)
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serializer = UserSerializer(user)
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return Response(serializer.data)
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If we need to, we can bind this viewset into two seperate views, like so:
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user_list = UserViewSet.as_view({'get': 'list'})
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user_detail = UserViewSet.as_view({'get': 'retrieve'})
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Typically we wouldn't do this, but would instead register the viewset with a router, and allow the urlconf to be automatically generated.
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router = DefaultRouter()
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router.register(r'users', UserViewSet, 'user')
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urlpatterns = router.urls
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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:
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class UserViewSet(viewsets.ModelViewSet):
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"""
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A viewset for viewing and editing user instances.
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"""
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serializer_class = UserSerializer
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queryset = User.objects.all()
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There are two main advantages of using a `ViewSet` class over using a `View` class.
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* Repeated logic can be combined into a single class. In the above example, we only need to specify the `queryset` once, and it'll be used across multiple views.
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* By using routers, we no longer need to deal with wiring up the URL conf ourselves.
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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.
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## Marking extra methods for routing
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The default routers included with REST framework will provide routes for a standard set of create/retrieve/update/destroy style operations, as shown below:
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class UserViewSet(viewsets.VietSet):
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"""
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Example empty viewset demonstrating the standard
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actions that will be handled by a router class.
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If you're using format suffixes, make sure to also include
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the `format=None` keyword argument for each action.
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"""
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def list(self, request):
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pass
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def create(self, request):
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pass
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def retrieve(self, request, pk=None):
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pass
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def update(self, request, pk=None):
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pass
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def partial_update(self, request, pk=None):
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pass
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def destroy(self, request, pk=None):
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pass
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If you have ad-hoc methods that you need to be routed to, you can mark them as requiring routing using the `@link` or `@action` decorators. The `@link` decorator will route `GET` requests, and the `@action` decroator will route `POST` requests.
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For example:
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from django.contrib.auth.models import User
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from rest_framework import viewsets
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from rest_framework.decorators import action
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from myapp.serializers import UserSerializer
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class UserViewSet(viewsets.ModelViewSet):
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"""
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A viewset that provides the standard actions
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"""
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queryset = User.objects.all()
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serializer_class = UserSerializer
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@action
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def set_password(self, request, pk=None):
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user = self.get_object()
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serializer = PasswordSerializer(data=request.DATA)
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if serializer.is_valid():
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user.set_password(serializer.data['password'])
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user.save()
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return Response({'status': 'password set'})
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else:
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return Response(serializer.errors,
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status=status.HTTP_400_BAD_REQUEST)
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The `@action` and `@link` decorators can additionally take extra arguments that will be set for the routed view only. For example...
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@action(permission_classes=[IsAdminOrIsSelf])
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def set_password(self, request, pk=None):
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...
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---
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# API Reference
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## ViewSet
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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.
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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.
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## ModelViewSet
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The `ModelViewSet` class inherits from `GenericAPIView` and includes implementations for various actions, by mixing in the behavior of the
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The actions provided by the `ModelViewSet` class are `.list()`, `.retrieve()`, `.create()`, `.update()`, and `.destroy()`.
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#### Example
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Because `ModelViewSet` extends `GenericAPIView`, you'll normally need to provide at least the `queryset` and `serializer_class` attributes. For example:
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class AccountViewSet(viewsets.ModelViewSet):
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"""
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A simple ViewSet for viewing and editing accounts.
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"""
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queryset = Account.objects.all()
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serializer_class = AccountSerializer
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permission_classes = [IsAccountAdminOrReadOnly]
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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:
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class AccountViewSet(viewsets.ModelViewSet):
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"""
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A simple ViewSet for viewing and editing the accounts
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associated with the user.
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"""
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serializer_class = AccountSerializer
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permission_classes = [IsAccountAdminOrReadOnly]
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def get_queryset(self):
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return request.user.accounts.all()
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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.
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## ReadOnlyModelViewSet
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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()`.
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#### Example
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As with `ModelViewSet`, you'll normally need to provide at least the `queryset` and `serializer_class` attributes. For example:
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class AccountViewSet(viewsets.ReadOnlyModelViewSet):
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"""
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A simple ViewSet for viewing accounts.
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"""
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queryset = Account.objects.all()
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serializer_class = AccountSerializer
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Again, as with `ModelViewSet`, you can use any of the standard attributes and method overrides available to `GenericAPIView`.
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# Custom ViewSet base classes
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Any standard `View` class can be turned into a `ViewSet` class by mixing in `ViewSetMixin`. You can use this to define your own base classes.
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## Example
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For example, we can create a base viewset class that provides `retrieve`, `update` and `list` operations:
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class RetrieveUpdateListViewSet(mixins.RetrieveModelMixin,
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mixins.UpdateModelMixin,
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mixins.ListModelMixin,
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viewsets.ViewSetMixin,
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generics.GenericAPIView):
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"""
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A viewset that provides `retrieve`, `update`, and `list` actions.
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To use it, override the class and set the `.queryset` and
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`.serializer_class` attributes.
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"""
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pass
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By creating your own base `ViewSet` classes, you can provide common behavior that can be reused in multiple views across your API.
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[cite]: http://guides.rubyonrails.org/routing.html
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