""" Basic building blocks for generic class based views. We don't bind behaviour to http method handlers yet, which allows mixin classes to be composed in interesting ways. """ from __future__ import unicode_literals from django.core.exceptions import ValidationError from django.http import Http404 from rest_framework import status from rest_framework.response import Response from rest_framework.request import clone_request import warnings def _get_validation_exclusions(obj, pk=None, slug_field=None, lookup_field=None): """ Given a model instance, and an optional pk and slug field, return the full list of all other field names on that model. For use when performing full_clean on a model instance, so we only clean the required fields. """ include = [] if pk: # Pending deprecation pk_field = obj._meta.pk while pk_field.rel: pk_field = pk_field.rel.to._meta.pk include.append(pk_field.name) if slug_field: # Pending deprecation include.append(slug_field) if lookup_field and lookup_field != 'pk': include.append(lookup_field) return [field.name for field in obj._meta.fields if field.name not in include] class CreateModelMixin(object): """ Create a model instance. """ def create(self, request, *args, **kwargs): serializer = self.get_serializer(data=request.DATA, files=request.FILES) if serializer.is_valid(): self.pre_save(serializer.object) self.object = serializer.save(force_insert=True) self.post_save(self.object, created=True) headers = self.get_success_headers(serializer.data) return Response(serializer.data, status=status.HTTP_201_CREATED, headers=headers) return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST) def get_success_headers(self, data): try: return {'Location': data['url']} except (TypeError, KeyError): return {} class ListModelMixin(object): """ List a queryset. """ empty_error = "Empty list and '%(class_name)s.allow_empty' is False." def list(self, request, *args, **kwargs): self.object_list = self.filter_queryset(self.get_queryset()) # Default is to allow empty querysets. This can be altered by setting # `.allow_empty = False`, to raise 404 errors on empty querysets. if not self.allow_empty and not self.object_list: warnings.warn( 'The `allow_empty` parameter is due to be deprecated. ' 'To use `allow_empty=False` style behavior, You should override ' '`get_queryset()` and explicitly raise a 404 on empty querysets.', PendingDeprecationWarning ) class_name = self.__class__.__name__ error_msg = self.empty_error % {'class_name': class_name} raise Http404(error_msg) # Switch between paginated or standard style responses page = self.paginate_queryset(self.object_list) if page is not None: serializer = self.get_pagination_serializer(page) else: serializer = self.get_serializer(self.object_list, many=True) return Response(serializer.data) class RetrieveModelMixin(object): """ Retrieve a model instance. """ def retrieve(self, request, *args, **kwargs): self.object = self.get_object() serializer = self.get_serializer(self.object) return Response(serializer.data) class UpdateModelMixin(object): """ Update a model instance. """ def update(self, request, *args, **kwargs): partial = kwargs.pop('partial', False) self.object = self.get_object_or_none() if self.object is None: created = True save_kwargs = {'force_insert': True} success_status_code = status.HTTP_201_CREATED else: created = False save_kwargs = {'force_update': True} success_status_code = status.HTTP_200_OK serializer = self.get_serializer(self.object, data=request.DATA, files=request.FILES, partial=partial) if serializer.is_valid(): try: self.pre_save(serializer.object) except ValidationError as err: # full_clean on model instance may be called in pre_save, so we # have to handle eventual errors. return Response(err.message_dict, status=status.HTTP_400_BAD_REQUEST) self.object = serializer.save(**save_kwargs) self.post_save(self.object, created=created) return Response(serializer.data, status=success_status_code) return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST) def partial_update(self, request, *args, **kwargs): kwargs['partial'] = True return self.update(request, *args, **kwargs) def get_object_or_none(self): try: return self.get_object() except Http404: if self.request.method == 'PUT': # For PUT-as-create operation, we need to ensure that we have # relevant permissions, as if this was a POST request. This # will either raise a PermissionDenied exception, or simply # return None. self.check_permissions(clone_request(self.request, 'POST')) else: # PATCH requests where the object does not exist should still # return a 404 response. raise def pre_save(self, obj): """ Set any attributes on the object that are implicit in the request. """ # pk and/or slug attributes are implicit in the URL. lookup_url_kwarg = self.lookup_url_kwarg or self.lookup_field lookup = self.kwargs.get(lookup_url_kwarg, None) pk = self.kwargs.get(self.pk_url_kwarg, None) slug = self.kwargs.get(self.slug_url_kwarg, None) slug_field = slug and self.slug_field or None if lookup: setattr(obj, self.lookup_field, lookup) if pk: setattr(obj, 'pk', pk) if slug: setattr(obj, slug_field, slug) # Ensure we clean the attributes so that we don't eg return integer # pk using a string representation, as provided by the url conf kwarg. if hasattr(obj, 'full_clean'): exclude = _get_validation_exclusions(obj, pk, slug_field, self.lookup_field) obj.full_clean(exclude) class DestroyModelMixin(object): """ Destroy a model instance. """ def destroy(self, request, *args, **kwargs): obj = self.get_object() self.pre_delete(obj) obj.delete() self.post_delete(obj) return Response(status=status.HTTP_204_NO_CONTENT)