What You Should Know About Django REST Framework Lacey Williams Henschel PyCascades, February 2021 @laceynwilliams | @revsys

What You Should Know About Django REST Framework: ViewSets Edition! @laceynwilliams | @revsys

ClassyDRF @laceynwilliams | @revsys

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DRF has good docs DRF Docs on ViewSets @laceynwilliams | @revsys

ModelViewSet @laceynwilliams | @revsys

ModelViewSet = set of views to: ✓ create ✓ retrieve ✓ update ✓ list ✓ destroy @laceynwilliams | @revsys

class ModelViewSet(mixins.CreateModelMixin, mixins.RetrieveModelMixin, mixins.UpdateModelMixin, mixins.DestroyModelMixin, mixins.ListModelMixin, GenericViewSet): """ A viewset that provides default `create()`, `retrieve()`, `update()`, `partial_update()`, `destroy()` and `list()` actions. """ pass @laceynwilliams | @revsys

Each *ModelMixin class has its own methods that perform the right ac4ons. CreateModelMixin has a create() method, instead of a post() method. @laceynwilliams | @revsys

This ViewSet... # views.py from rest_framework.viewsets import ModelViewSet from .models import Book from .serializers import BookSerializer class BookViewSet(ModelViewSet): queryset = Book.objects.all() serializer_class = BookSerializer @laceynwilliams | @revsys

...gives us these endpoints1 GET /books/ GET /books/{id}/ POST /books/ PUT /books/{id}/ PATCH /books/{id}/ DELETE /books/{id}/ 1 you also need to hook the ViewSet to your urls @laceynwilliams | @revsys

A"ributes for your ModelViewSet @laceynwilliams | @revsys

What objects are you working with? from rest_framework.permissions import AllowAny from rest_framework.viewsets import ModelViewSet from .models import Book from .serializers import BookSerializer class BookViewSet(ModelViewSet): queryset = Book.objects.all() serializer_class = BookSerializer permission_classes = [AllowAny] @laceynwilliams | @revsys

How should the data be serialized? from rest_framework.permissions import AllowAny from rest_framework.viewsets import ModelViewSet from .models import Book from .serializers import BookSerializer class BookViewSet(ModelViewSet): queryset = Book.objects.all() serializer_class = BookSerializer permission_classes = [AllowAny] @laceynwilliams | @revsys

Who is allowed? from rest_framework.permissions import AllowAny from rest_framework.viewsets import ModelViewSet from .models import Book from .serializers import BookSerializer class BookViewSet(ModelViewSet): queryset = Book.objects.all() serializer_class = BookSerializer permission_classes = [AllowAny] @laceynwilliams | @revsys

Methods that come from GenericAPIView @laceynwilliams | @revsys

def get_queryset(self): assert self.queryset is not None, ( "'%s' should either include a `queryset` attribute, " "or override the `get_queryset()` method." % self.__class__.__name__ ) queryset = self.queryset if isinstance(queryset, QuerySet): queryset = queryset.all() return queryset @laceynwilliams | @revsys

When to override get_queryset(): When you need to filter your queryset with data you don't have un5l the 5me of the request (like filter by user) @laceynwilliams | @revsys

def get_object(self): queryset = self.filter_queryset(self.get_queryset()) lookup_url_kwarg = self.lookup_url_kwarg or self.lookup_field assert lookup_url_kwarg in self.kwargs, ( 'Expected view %s to be called with a URL keyword argument ' 'named "%s". Fix your URL conf, or set the `.lookup_field` ' 'attribute on the view correctly.' % (self.__class__.__name__, lookup_url_kwarg) ) # Uses the lookup_field attribute, which defaults to `pk` filter_kwargs = {self.lookup_field: self.kwargs[lookup_url_kwarg]} obj = get_object_or_404(queryset, **filter_kwargs) # May raise a permission denied self.check_object_permissions(self.request, obj) return obj @laceynwilliams | @revsys

In your own methods, you can run: obj = self.get_object() instead of looking up the object yourself. @laceynwilliams | @revsys

def get_serializer_class(self): assert self.serializer_class is not None, ( "'%s' should either include a `serializer_class` attribute, " "or override the `get_serializer_class()` method." % self.__class__.__name__ ) # Returns the attribute you set return self.serializer_class @laceynwilliams | @revsys

When to override get_serializer_class(): When you want to use different serializers in different situa3ons @laceynwilliams | @revsys

def get_serializer(self, *args, **kwargs): serializer_class = self.get_serializer_class() # The context is where the request is added # to the serializer kwargs['context'] = self.get_serializer_context() return serializer_class(*args, **kwargs) @laceynwilliams | @revsys

def get_serializer(self, *args, **kwargs): serializer_class = self.get_serializer_class() # The context is where the request is added # to the serializer kwargs['context'] = self.get_serializer_context() return serializer_class(*args, **kwargs) @laceynwilliams | @revsys

def get_serializer_context(self): # Override this method to add more stuff # to the serializer context return { 'request': self.request, 'format': self.format_kwarg, 'view': self } @laceynwilliams | @revsys

When to override get_serializer_context(): When you need to add something to the context so your serializer can use it @laceynwilliams | @revsys

In your methods, you can run: serializer = self.get_serializer() instead of accessing your serializer directly. @laceynwilliams | @revsys

Methods that come with the mixins for ModelViewSet @laceynwilliams | @revsys

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class CreateModelMixin: def create(self, request, *args, **kwargs): serializer = self.get_serializer(data=request.data) serializer.is_valid(raise_exception=True) self.perform_create(serializer) headers = self.get_success_headers(serializer.data) return Response( serializer.data, status=status.HTTP_201_CREATED, headers=headers ) @laceynwilliams | @revsys

class CreateModelMixin: def create(self, request, *args, **kwargs): serializer = self.get_serializer(data=request.data) serializer.is_valid(raise_exception=True) self.perform_create(serializer) headers = self.get_success_headers(serializer.data) return Response( serializer.data, status=status.HTTP_201_CREATED, headers=headers ) @laceynwilliams | @revsys

class CreateModelMixin: def create(self, request, *args, **kwargs): serializer = self.get_serializer(data=request.data) serializer.is_valid(raise_exception=True) self.perform_create(serializer) headers = self.get_success_headers(serializer.data) return Response( serializer.data, status=status.HTTP_201_CREATED, headers=headers ) @laceynwilliams | @revsys

class CreateModelMixin: def perform_create(self, serializer): serializer.save() @laceynwilliams | @revsys

class CreateModelMixin: def create(self, request, *args, **kwargs): serializer = self.get_serializer(data=request.data) serializer.is_valid(raise_exception=True) self.perform_create(serializer) headers = self.get_success_headers(serializer.data) return Response( serializer.data, status=status.HTTP_201_CREATED, headers=headers ) @laceynwilliams | @revsys

... Why did you show me a bunch of source code? @laceynwilliams | @revsys

"I want my books to have a lot of data for the detail endpoints, but only some of the data for the list endpoint. Can I do that?" @laceynwilliams | @revsys

from rest_framework.permissions import AllowAny from rest_framework.viewsets import ModelViewSet from .models import Book from .serializers import BookDetailSerializer, BookListSerializer class BookViewSet(ModelViewSet): queryset = Book.objects.all() serializer_class = BookDetailSerializer permission_classes = [AllowAny] def get_serializer_class(self): if self.action in ["list"]: return BookListSerializer return super().get_serializer_class() @laceynwilliams | @revsys

"A#er I create a book, I want to use a different, more detailed serializer to return it." @laceynwilliams | @revsys

Reminder class CreateModelMixin: def create(self, request, *args, **kwargs): serializer = self.get_serializer(data=request.data) serializer.is_valid(raise_exception=True) self.perform_create(serializer) headers = self.get_success_headers(serializer.data) return Response( serializer.data, status=status.HTTP_201_CREATED, headers=headers ) @laceynwilliams | @revsys

Reminder class CreateModelMixin: def create(self, request, *args, **kwargs): serializer = self.get_serializer(data=request.data) serializer.is_valid(raise_exception=True) self.perform_create(serializer) headers = self.get_success_headers(serializer.data) return Response( serializer.data, status=status.HTTP_201_CREATED, headers=headers ) @laceynwilliams | @revsys

from rest_framework.permissions import AllowAny from rest_framework.viewsets import ModelViewSet from .models import Book from .serializers import BookSerializer, BookCreatedSerializer class BookViewSet(ModelViewSet): ... def create(self, request, *args, **kwargs): serializer = self.get_serializer(data=request.data) serializer.is_valid(raise_exception=True) # self.perform_create(serializer) instance = serializer.save() return_serializer = BookCreatedSerializer(instance) headers = self.get_success_headers(return_serializer.data) return Response( return_serializer.data, status=status.HTTP_201_CREATED, headers=headers ) @laceynwilliams | @revsys

from rest_framework.permissions import AllowAny from rest_framework.viewsets import ModelViewSet from .models import Book from .serializers import BookSerializer, BookCreatedSerializer class BookViewSet(ModelViewSet): ... def create(self, request, *args, **kwargs): serializer = self.get_serializer(data=request.data) serializer.is_valid(raise_exception=True) # self.perform_create(serializer) instance = serializer.save() return_serializer = BookCreatedSerializer(instance) headers = self.get_success_headers(return_serializer.data) return Response( return_serializer.data, status=status.HTTP_201_CREATED, headers=headers ) @laceynwilliams | @revsys

from rest_framework.permissions import AllowAny from rest_framework.viewsets import ModelViewSet from .models import Book from .serializers import BookSerializer, BookCreatedSerializer class BookViewSet(ModelViewSet): ... def create(self, request, *args, **kwargs): serializer = self.get_serializer(data=request.data) serializer.is_valid(raise_exception=True) # self.perform_create(serializer) instance = serializer.save() return_serializer = BookCreatedSerializer(instance) headers = self.get_success_headers(return_serializer.data) return Response( return_serializer.data, status=status.HTTP_201_CREATED, headers=headers ) @laceynwilliams | @revsys

"But I don't need ALL those endpoints. Only most of them." @laceynwilliams | @revsys

Do everything except delete from rest_framework.generics import GenericAPIView from rest_framework.mixins import CreateModelMixin, RetrieveModelMixin, UpdateModelMixin, ListModelMixin # import models and serializers... class BookViewSet( CreateModelMixin, RetrieveModelMixin, UpdateModelMixin, ListModelMixin, GenericAPIView ): ... @laceynwilliams | @revsys

DRF mixes and matches for you ✓ UpdateAPIView = UpdateModelMixin + GenericAPIView ✓ CreateAPIView ✓ ListAPIView ✓ RetrieveAPIView ✓ DestroyAPIView ✓ ReadOnlyModelViewSet ✓ RetrieveDestroyAPIView ✓ RetrieveUpdateDestroy APIView ✓ ListCreateAPIView ✓ RetrieveUpdateAPIView @laceynwilliams | @revsys

"Can we have an endpoint that just shows our featured books?" @laceynwilliams | @revsys

from rest_framework.decorators import action class BookViewSet(ModelViewSet): queryset = Book.objects.all() serializer_class = BookDetailSerializer def get_serializer_class(self): if self.action in ["list", "featured"]: return BookListSerializer return super().get_serializer_class() @action(detail=False, methods=["get"]) def featured(self, request): books = self.get_queryset().filter(featured=True) serializer = self.get_serializer(books, many=True) return Response(serializer.data, status=status.HTTP_200_OK) @laceynwilliams | @revsys

from rest_framework.decorators import action class BookViewSet(ModelViewSet): queryset = Book.objects.all() serializer_class = BookDetailSerializer def get_serializer_class(self): if self.action in ["list", "featured"]: return BookListSerializer return super().get_serializer_class() @action(detail=False, methods=["get"]) def featured(self, request): books = self.get_queryset().filter(featured=True) serializer = self.get_serializer(books, many=True) return Response(serializer.data, status=status.HTTP_200_OK) @laceynwilliams | @revsys

url = GET /books/featured/ @laceynwilliams | @revsys

from rest_framework.decorators import action class BookViewSet(ModelViewSet): queryset = Book.objects.all() serializer_class = BookDetailSerializer def get_serializer_class(self): if self.action in ["list", "featured"]: return BookListSerializer return super().get_serializer_class() @action(detail=False, methods=["get"]) def featured(self, request): books = self.get_queryset().filter(featured=True) serializer = self.get_serializer(books, many=True) return Response(serializer.data, status=status.HTTP_200_OK) @laceynwilliams | @revsys

from rest_framework.decorators import action class BookViewSet(ModelViewSet): queryset = Book.objects.all() serializer_class = BookDetailerializer def get_serializer_class(self): if self.action in ["list", "featured"]: return BookListSerializer return super().get_serializer_class() @action(detail=False, methods=["get"]) def featured(self, request): books = self.get_queryset().filter(featured=True) serializer = self.get_serializer(books, many=True) return Response(serializer.data, status=status.HTTP_200_OK) @laceynwilliams | @revsys

from rest_framework.decorators import action class BookViewSet(ModelViewSet): queryset = Book.objects.all() serializer_class = BookDetailerializer def get_serializer_class(self): if self.action in ["list", "featured"]: return BookListSerializer return super().get_serializer_class() @action(detail=False, methods=["get"]) def featured(self, request): books = self.get_queryset().filter(featured=True) serializer = self.get_serializer(books, many=True) return Response(serializer.data, status=status.HTTP_200_OK) @laceynwilliams | @revsys

Thank you! To Tom Chris*e and the maintainers of DRF. To Vinta So*ware and the maintainers of Classy DRF. To Beki Post and Jeff Triple3 for their help with this talk. To Vancouver PyLadies for le4ng me preview this talk with you. To PyCascades! @laceynwilliams | @revsys

✉ lacey@revsys.com " @laceynwilliams # laceyhenschel.com # revsys.com @laceynwilliams | @revsys