# REST framework 2.3 announcement

REST framework 2.3 is geared towards making it easier and quicker to build your Web APIs.

## ViewSets & Routers

**TODO**

## Easier Serializers

REST framework lets you be totally explict regarding how you want to represent relationships, allowing you to choose between styles such as hyperlinking or primary key relationships.

The ability to specify exactly how you want to represent relationships is powerful, but it also introduces complexity.  In order to keep things more simple, REST framework now allows you to include reverse relationships simply by including the field name in the `fields` metadata of the serializer class.

For example, in REST framework 2.2, reverse relationships needed to be included explicitly on a serializer class.

    class BlogSerializer(serializers.ModelSerializer):
        comments = serializers.PrimaryKeyRelatedField(many=True)

        class Meta:
            model = Blog
            fields = ('id', 'title', 'created', 'comments')

As of 2.3, you can simply include the field name, and the appropriate serializer field will automatically be used for the relationship.

    class BlogSerializer(serializers.ModelSerializer):
        """
        Don't need to specify the 'comments' field explicitly anymore.
        """
        class Meta:
            model = Blog
            fields = ('id', 'title', 'created', 'comments')

Similarly, you can now easily include the primary key in hyperlinked relationships, simply by adding the field name to the metadata.

    class BlogSerializer(serializers.HyperlinkedModelSerializer):
        """
        This is a hyperlinked serializer, which default to using
        a field named 'url' as the primary identifier.
        Note that we can now easily also add in the 'id' field.
        """
        class Meta:
            model = Blog
            fields = ('url', 'id', 'title', 'created', 'comments')

## Simpler views

This release rationalises the API and implementation of the generic views, dropping the dependancy on Django's `SingleObjectMixin` and `MultipleObjectMixin` classes, removing a number of unneeded attributes, and generally making the implementation more obvious and easy to work with.

This improvement is reflected in improved documentation for the `GenericAPIView` base class, and should make it easier to determine how to override methods on the base class if you need to write customized subclasses.

---

# API Changes

## Simplified generic view classes

The functionality provided by `SingleObjectAPIView` and `MultipleObjectAPIView` base classes has now been moved into the base class `GenericAPIView`.  The implementation of this base class is simple enough that providing subclasses for the base classes of detail and list views is somewhat unnecessary.

Additionally the base generic view no longer inherits from Django's `SingleObjectMixin` or `MultipleObjectMixin` classes, simplifying the implementation, and meaning you don't need to cross-reference across to Django's codebase.

Using the `SingleObjectAPIView` and `MultipleObjectAPIView` base classes continues to be supported, but will raise a `PendingDeprecationWarning`.  You should instead simply use `GenericAPIView` as the base for any generic view subclasses.

### Removed attributes

The following attributes and methods, were previously present as part of Django's generic view implementations, but were unneeded and unusedand have now been entirely removed.

* context_object_name
* get_context_data()
* get_context_object_name()

The following attributes and methods, which were previously present as part of Django's generic view implementations have also been entirely removed.

* paginator_class
* get_paginator()
* get_allow_empty()
* get_slug_field()

There may be cases when removing these bits of API might mean you need to write a little more code if your view has highly customized behavior, but generally we believe that providing a coarser-grained API will make the views easier to work with, and is the right trade-off to make for the vast majority of cases.

Note that the listed attributes and methods have never been a documented part of the REST framework API, and as such are not covered by the deprecation policy.

### Simplified methods

The `get_object` and `get_paginate_by` methods no longer take an optional queryset argument.  This makes overridden these methods more obvious, and a little more simple.

Using an optional queryset with these methods continues to be supported, but will raise a `PendingDeprecationWarning`.

The `paginate_queryset` method no longer takes a `page_size` argument, or returns a four-tuple of pagination information.  Instead it simply takes a queryset argument, and either returns a `page` object with an appropraite page size, or returns `None`, if pagination is not configured for the view.

Using the `page_size` argument is still supported and will trigger the old-style return type, but will raise a `PendingDeprecationWarning`.

### Deprecated attributes

The following attributes are used to control queryset lookup, and have all been moved into a pending deprecation state.

* pk_url_kwarg = 'pk'
* slug_url_kwarg = 'slug'
* slug_field = 'slug'

Their usage is replaced with a single attribute:

* lookup_field = 'pk'

This attribute is used both as the regex keyword argument in the URL conf, and as the model field to filter against when looking up a model instance.  To use non-pk based lookup, simply set the `lookup_field` argument to an alternative field, and ensure that the keyword argument in the url conf matches the field name.

For example, a view with 'username' based lookup might look like this:

    class UserDetail(generics.RetrieveAPIView):
        lookup_field = 'username'
        queryset = User.objects.all()
        serializer_class = UserSerializer

And would have the following entry in the urlconf:

     url(r'^users/(?P<username>\w+)/$', UserDetail.as_view()),


Usage of the old-style attributes continues to be supported, but will raise a `PendingDeprecationWarning`.

## DecimalField

2.3 introduces a `DecimalField` serializer field, which returns `Decimal` instances.

For most cases APIs using model fields will behave as previously, however if you are using a custom renderer, not provided by REST framework, then you may now need to add support for rendering `Decimal` instances to your renderer implmentation.

---

# Other notes

## Explict view attributes

The usage of `model` attribute in generic Views is still supported, but it's usage is being discouraged in favour of using explict `queryset` and `serializer_class` attributes.

For example, the following is now the recommended style for using generic views:

    class AccountListView(generics.RetrieveAPIView):
        queryset = MyModel.objects.all()
        serializer_class = MyModelSerializer

Using explict `queryset` and `serializer_class` attributes makes the functioning of the view more clear than using the shortcut `model` attribute.

It also makes it the usage of overridden `get_queryset()` or `get_serializer_class()` methods more obvious.

    class AccountListView(generics.RetrieveAPIView):
        serializer_class = MyModelSerializer

        def get_queryset(self):
            """
            Determine the queryset dynamically, depending on the
            user making the request.

            Note that overriding this method follows on more obviously now
            that an explicit `queryset` attribute is the usual view style.
            """
            return self.user.accounts

## Django 1.3 support

The 2.3 release series will be the last series to provide compatiblity with Django 1.3.

## What comes next?

The plan for the next few months is to concentrate on addressing outstanding tickets.  2.4 is likely to deal with relatively small refinements to the existing API.