"""
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)