From 48b02f016a827bc254aba2aedb81b472189c2165 Mon Sep 17 00:00:00 2001 From: Kyle Valade Date: Sun, 27 Jul 2014 14:01:43 -0700 Subject: [PATCH 1/3] Issue #1707: Add documentation to api-docs.viewsets notifying users that they should use the get_queryset() method when overriding a ModelViewSet method, such as list(). Otherwise, since queryset is a static property, the value will be cached for every instance of that ViewSet. --- docs/api-guide/viewsets.md | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/docs/api-guide/viewsets.md b/docs/api-guide/viewsets.md index 23b16575f..774e11b76 100644 --- a/docs/api-guide/viewsets.md +++ b/docs/api-guide/viewsets.md @@ -70,6 +70,21 @@ There are two main advantages of using a `ViewSet` class over using a `View` cla 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. +## Overriding ModelViewSet Methods + +Overriding the ModelViewSet is the same as overriding anything else, except you will need to remember to clone `self.queryset` before you use it, which you can do by using the built-in `get_queryset` method. For example: + + class UserViewSet(viewsets.ModelViewSet): + """ + A viewset for viewing and editing user instances. + """ + queryset = User.objects.all() + + def list(self, request): + queryset = self.get_queryset() + serializer = UserSerializer(queryset, many=True) + return Response(serializer.data) + ## Marking extra methods 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: @@ -142,7 +157,7 @@ The `@action` decorator will route `POST` requests by default, but may also acce @action(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/$` and `^users/{pk}/unset_password/$` From e40ffd60d44d736d7e27ff454cba1905f0becc26 Mon Sep 17 00:00:00 2001 From: Kyle Date: Mon, 28 Jul 2014 10:11:40 -0700 Subject: [PATCH 2/3] Issue #1707 - Add documentation about the caching of `GenericAPIView.queryset` to the `queryset` property, `get_queryset()`, and do generic-views.md; remove changes to the viewsets.md documentation from my last commit. --- docs/api-guide/generic-views.md | 8 +++++++- docs/api-guide/viewsets.md | 15 --------------- rest_framework/generics.py | 8 ++++++++ 3 files changed, 15 insertions(+), 16 deletions(-) diff --git a/docs/api-guide/generic-views.md b/docs/api-guide/generic-views.md index 7d06f246c..b76c18cf5 100755 --- a/docs/api-guide/generic-views.md +++ b/docs/api-guide/generic-views.md @@ -43,6 +43,12 @@ For more complex cases you might also want to override various methods on the vi return 20 return 100 + def list(self, request): + # Note the use of `get_queryset()` instead of `self.queryset` + queryset = self.get_queryset() + serializer = UserSerializer(queryset, many=True) + return Response(serializer.data) + For very simple cases you might want to pass through any class attributes using the `.as_view()` method. For example, your URLconf might include something the following entry. url(r'^/users/', ListCreateAPIView.as_view(model=User), name='user-list') @@ -63,7 +69,7 @@ Each of the concrete generic views provided is built by combining `GenericAPIVie The following attributes control the basic view behavior. -* `queryset` - The queryset that should be used for returning objects from this view. Typically, you must either set this attribute, or override the `get_queryset()` method. +* `queryset` - The queryset that should be used for returning objects from this view. Typically, you must either set this attribute, or override the `get_queryset()` method. If you are overriding a view method, it is important that you call `get_queryset()` instead of accessing this property directly, as `queryset` will get evaluated once, and those results will be cached for all subsequent requests. * `serializer_class` - The serializer class that should be used for validating and deserializing input, and for serializing output. Typically, you must either set this attribute, or override the `get_serializer_class()` method. * `lookup_field` - The model field that should be used to for performing object lookup of individual model instances. Defaults to `'pk'`. Note that when using hyperlinked APIs you'll need to ensure that *both* the API views *and* the serializer classes set the lookup fields if you need to use a custom value. * `lookup_url_kwarg` - The URL keyword argument that should be used for object lookup. The URL conf should include a keyword argument corresponding to this value. If unset this defaults to using the same value as `lookup_field`. diff --git a/docs/api-guide/viewsets.md b/docs/api-guide/viewsets.md index 774e11b76..4f345abba 100644 --- a/docs/api-guide/viewsets.md +++ b/docs/api-guide/viewsets.md @@ -70,21 +70,6 @@ There are two main advantages of using a `ViewSet` class over using a `View` cla 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. -## Overriding ModelViewSet Methods - -Overriding the ModelViewSet is the same as overriding anything else, except you will need to remember to clone `self.queryset` before you use it, which you can do by using the built-in `get_queryset` method. For example: - - class UserViewSet(viewsets.ModelViewSet): - """ - A viewset for viewing and editing user instances. - """ - queryset = User.objects.all() - - def list(self, request): - queryset = self.get_queryset() - serializer = UserSerializer(queryset, many=True) - return Response(serializer.data) - ## Marking extra methods 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: diff --git a/rest_framework/generics.py b/rest_framework/generics.py index 7bac510f7..65ccd9521 100644 --- a/rest_framework/generics.py +++ b/rest_framework/generics.py @@ -43,6 +43,10 @@ class GenericAPIView(views.APIView): # You'll need to either set these attributes, # or override `get_queryset()`/`get_serializer_class()`. + # If you are overriding a view method, it is important that you call + # `get_queryset()` instead of accessing the `queryset` property directly, + # as `queryset` will get evaluated only once, and those results are cached + # for all subsequent requests. queryset = None serializer_class = None @@ -256,6 +260,10 @@ class GenericAPIView(views.APIView): This must be an iterable, and may be a queryset. Defaults to using `self.queryset`. + This method should always be used rather than accessing `self.queryset` + directly, as `self.queryset` gets evaluated only once, and those results + are cached for all subsequent requests. + You may want to override this if you need to provide different querysets depending on the incoming request. From fc8eb76c2259ea64a19876f040db4d93e834d39d Mon Sep 17 00:00:00 2001 From: Kyle Date: Mon, 28 Jul 2014 10:19:42 -0700 Subject: [PATCH 3/3] Issue #1707 - Add info about queryset property caching to get_queryset() docs. Add documentation to the get_queryset() method of generic-views.md regarding the caching of the queryset property. --- docs/api-guide/generic-views.md | 2 ++ 1 file changed, 2 insertions(+) diff --git a/docs/api-guide/generic-views.md b/docs/api-guide/generic-views.md index b76c18cf5..43c5782f4 100755 --- a/docs/api-guide/generic-views.md +++ b/docs/api-guide/generic-views.md @@ -99,6 +99,8 @@ The following attributes are used to control pagination when used with list view Returns the queryset that should be used for list views, and that should be used as the base for lookups in detail views. Defaults to returning the queryset specified by the `queryset` attribute, or the default queryset for the model if the `model` shortcut is being used. +This method should always be used rather than accessing `self.queryset` directly, as `self.queryset` gets evaluated only once, and those results are cached for all subsequent requests. + May be overridden to provide dynamic behavior such as returning a queryset that is specific to the user making the request. For example: