drf-generic views 쉽게 해석

Generic views

" Django’s generic views... were developed as a shortcut for common usage patterns... They take certain common idioms and patterns found in view development and abstract them so that you can quickly write common views of data without having to repeat yourself."

— Django Documentation

django의 generic views는 공통적으로 사용되는 패턴을 줄이기 위해 개발되었다. generic views는 view 개발에서 어떤 공통된 관용구와 패턴들을 추상화 하였다 그 결과 당신은 빠르게 공통된 데이터 views를 code할수 있다 반복되는 작업 없이
- Django Documentation

One of the key benefits of class-based views is the way they allow you to compose bits of reusable behavior. REST framework takes advantage of this by providing a number of pre-built views that provide for commonly used patterns.

class 기반으로 views의 중요 이점 중 하나는 재사용 가능한 코드로 작성할 수 있도록 도와준다. REST framework는 일반적으로 쓰이는 패턴들을 추상화하여 제공한다 (pre-built views라고 말하는 듯) 이러한 이점들을 취한다.(* 추상화라는 건 공통적인(일반적으로 반복되는 것들을 추출하여 코드를 하나로 표현하여 재사용성, 가독성 등을 높힘)

The generic views provided by REST framework allow you to quickly build API views that map closely to your database models.

If the generic views don't suit the needs of your API, you can drop down to using the regular APIView class, or reuse the mixins and base classes used by the generic views to compose your own set of reusable generic views.

generic views는 API views (database model에 근접하게 매핑되는)를 빠르게 code를 짤 수 있게 한다.
generic view가 필요하지 않다면 APIView class or mixins class or base classes 를 사용하여라

Examples

Typically when using the generic views, you'll override the view, and set several class attributes.

일반적으로 generic views를 쓸 때 여러 class들을 상속 받을 것이다

from django.contrib.auth.models import User
from myapp.serializers import UserSerializer
from rest_framework import generics
from rest_framework.permissions import IsAdminUser

class UserList(generics.ListCreateAPIView):
	# model 을 잡아줘야 해요
    queryset = User.objects.all()
    # User list를 위해 작성된 Userserializer
    serializer_class = UserSerializer
    permission_classes = [IsAdminUser]
    

For more complex cases you might also want to override various methods on the view class. For example.

class UserList(generics.ListCreateAPIView):
    queryset = User.objects.all()
    serializer_class = UserSerializer
    permission_classes = [IsAdminUser]
	
    
    def list(self, request):
        # Note the use of `get_queryset()` instead of `self.queryset`
        # self.queryset 대신에 get_queryset()을 잡아준 이유는
        # 비지니스 로직에 따라 잡아줘야할 queryset이 다르기 때문에
        # self.get_queryset() 함수를 호출한 것 같다
        queryset = self.get_queryset()
        # many 옵션은 복수 일때 붙혀준다.
        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 like the following entry:

보통 아래 url 과 같이 쓰지 않습니다(저는) 간단한 경우에 class 속성을 넣어줄 수 있습니다. 여기서 주목할 것은
.as_view()를 쎃다는 것인데요

django에서 보통 저희는 views.py에 있는 함수를 import 했습니다.
그런데 DRF에서 apis.py(=views.py)에서는 class를 선언해 주어 .as_view() 클래스 속성함수를 사용하여 마법처럼 함수들을 호출하게 됩니다.

url(r'^/users/', ListCreateAPIView.as_view(queryset=User.objects.all(), serializer_class=UserSerializer), name='user-list')

API Reference

GenericAPIView

This class extends REST framework's APIView class, adding commonly required behavior for standard list and detail views.

APIView class에서 확장된 개념이 genericAPI view입니다 필수적으로 list 와 detail페이지를 보여주는 것을 요구합니다.

Each of the concrete generic views provided is built by combining GenericAPIView, with one or more mixin classes.

Attributes

Basic settings:

The following attributes control the basic view behavior.

기본 속성들을 설명한다.

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.

view에서 queryset 일반적으로 설정 해줘야 합니다.
get_queryset() 함수를 이용하여 간접적으로 비지니스 로직에 따라 queryset을 설정하기도 합니다. 이러한 결과는 모두 subsequent requests에 따라 cached 됩니다.

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.

serializers.py 에 설정된 serializers 중에 하나를 get_serializer_class() 함수를 통해 잡아주어서 serializing or deserializing or validating할 때 사용합니다.

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.

pk or username 과 같은 값을 이용하여 model의 Instance를 잡아주는 것 같다 (ex. User.objects.get(pk=pk)

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.

Pagination:

The following attributes are used to control pagination when used with list views.

목록 보기에서 페이지에 보여질 개수를 control한다.

pagination_class

The pagination class that should be used when paginating list results. Defaults to the same value as the DEFAULT_PAGINATION_CLASS setting, which is 'rest_framework.pagination.PageNumberPagination'. Setting pagination_class=None will disable pagination on this view.

list 결과들을 페이지 매김을 할 때 사용 되어진다.
DEFAULT_PAGINATION_CLASS 기본 설정값이다.
pagination_class=None 으로 설정하면 페이지 매김이 비활성 화 된다.

Filtering:

filter_backends

A list of filter backend classes that should be used for filtering the queryset. Defaults to the same value as the DEFAULT_FILTER_BACKENDS setting.

queryset을 필터링하여 모델 instance를 필터하여 가져온다.

Methods

Base methods:

get_queryset(self)

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.

list views를 위해 사용되어지는 queryset을 반환한다 그리고 detail views에서 찾는 목적으로 사용 되어진다

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.

직접적으로 self.queryset에 접근하지 않고 간접적으로 get_queryset()을 사용 하며 한번 평가되어 진다.

May be overridden to provide dynamic behavior, such as returning a queryset, that is specific to the user making the request.

For example:

def get_queryset(self):
    user = self.request.user
    return user.accounts.all()

get_object(self)

Returns an object instance that should be used for detail views. Defaults to using the lookup_field parameter to filter the base queryset.

May be overridden to provide more complex behavior, such as object lookups based on more than one URL kwarg.

For example:

def get_object(self):
queryset = self.get_queryset()
filter = {}
for field in self.multiple_lookup_fields:
filter[field] = self.kwargs[field]

obj = get_object_or_404(queryset, **filter)
self.check_object_permissions(self.request, obj)
return obj

Note that if your API doesn't include any object level permissions, you may optionally exclude the self.check_object_permissions, and simply return the object from the get_object_or_404 lookup.

filter_queryset(self, queryset)
Given a queryset, filter it with whichever filter backends are in use, returning a new queryset.

For example:

def filter_queryset(self, queryset):
filter_backends = [CategoryFilter]

if 'geo_route' in self.request.query_params:
    filter_backends = [GeoRouteFilter, CategoryFilter]
elif 'geo_point' in self.request.query_params:
    filter_backends = [GeoPointFilter, CategoryFilter]

for backend in list(filter_backends):
    queryset = backend().filter_queryset(self.request, queryset, view=self)

return queryset

get_serializer_class(self)
Returns the class that should be used for the serializer. Defaults to returning the serializer_class attribute.

May be overridden to provide dynamic behavior, such as using different serializers for read and write operations, or providing different serializers to different types of users.

For example:

def get_serializer_class(self):
if self.request.user.is_staff:
return FullAccountSerializer
return BasicAccountSerializer
Save and deletion hooks:

The following methods are provided by the mixin classes, and provide easy overriding of the object save or deletion behavior.

perform_create(self, serializer) - Called by CreateModelMixin when saving a new object instance.
perform_update(self, serializer) - Called by UpdateModelMixin when saving an existing object instance.
perform_destroy(self, instance) - Called by DestroyModelMixin when deleting an object instance.
These hooks are particularly useful for setting attributes that are implicit in the request, but are not part of the request data. For instance, you might set an attribute on the object based on the request user, or based on a URL keyword argument.

def perform_create(self, serializer):
serializer.save(user=self.request.user)
These override points are also particularly useful for adding behavior that occurs before or after saving an object, such as emailing a confirmation, or logging the update.

def perform_update(self, serializer):
instance = serializer.save()
send_email_confirmation(user=self.request.user, modified=instance)
You can also use these hooks to provide additional validation, by raising a ValidationError(). This can be useful if you need some validation logic to apply at the point of database save. For example:

def perform_create(self, serializer):
queryset = SignupRequest.objects.filter(user=self.request.user)
if queryset.exists():
raise ValidationError('You have already signed up')
serializer.save(user=self.request.user)
Other methods:

You won't typically need to override the following methods, although you might need to call into them if you're writing custom views using GenericAPIView.

get_serializer_context(self) - Returns a dictionary containing any extra context that should be supplied to the serializer. Defaults to including 'request', 'view' and 'format' keys.
get_serializer(self, instance=None, data=None, many=False, partial=False) - Returns a serializer instance.
get_paginated_response(self, data) - Returns a paginated style Response object.
paginate_queryset(self, queryset) - Paginate a queryset if required, either returning a page object, or None if pagination is not configured for this view.
filter_queryset(self, queryset) - Given a queryset, filter it with whichever filter backends are in use, returning a new queryset.
Mixins
The mixin classes provide the actions that are used to provide the basic view behavior. Note that the mixin classes provide action methods rather than defining the handler methods, such as .get() and .post(), directly. This allows for more flexible composition of behavior.

The mixin classes can be imported from rest_framework.mixins.

ListModelMixin
Provides a .list(request, *args, **kwargs) method, that implements listing a queryset.

If the queryset is populated, this returns a 200 OK response, with a serialized representation of the queryset as the body of the response. The response data may optionally be paginated.

CreateModelMixin
Provides a .create(request, *args, **kwargs) method, that implements creating and saving a new model instance.

If an object is created this returns a 201 Created response, with a serialized representation of the object as the body of the response. If the representation contains a key named url, then the Location header of the response will be populated with that value.

If the request data provided for creating the object was invalid, a 400 Bad Request response will be returned, with the error details as the body of the response.

RetrieveModelMixin
Provides a .retrieve(request, *args, **kwargs) method, that implements returning an existing model instance in a response.

If an object can be retrieved this returns a 200 OK response, with a serialized representation of the object as the body of the response. Otherwise it will return a 404 Not Found.

UpdateModelMixin
Provides a .update(request, *args, **kwargs) method, that implements updating and saving an existing model instance.

Also provides a .partial_update(request, *args, **kwargs) method, which is similar to the update method, except that all fields for the update will be optional. This allows support for HTTP PATCH requests.

If an object is updated this returns a 200 OK response, with a serialized representation of the object as the body of the response.

If the request data provided for updating the object was invalid, a 400 Bad Request response will be returned, with the error details as the body of the response.

DestroyModelMixin
Provides a .destroy(request, *args, **kwargs) method, that implements deletion of an existing model instance.

If an object is deleted this returns a 204 No Content response, otherwise it will return a 404 Not Found.

Concrete View Classes
The following classes are the concrete generic views. If you're using generic views this is normally the level you'll be working at unless you need heavily customized behavior.

The view classes can be imported from rest_framework.generics.

CreateAPIView
Used for create-only endpoints.

Provides a post method handler.

Extends: GenericAPIView, CreateModelMixin

ListAPIView
Used for read-only endpoints to represent a collection of model instances.

Provides a get method handler.

Extends: GenericAPIView, ListModelMixin

RetrieveAPIView
Used for read-only endpoints to represent a single model instance.

Provides a get method handler.

Extends: GenericAPIView, RetrieveModelMixin

DestroyAPIView
Used for delete-only endpoints for a single model instance.

Provides a delete method handler.

Extends: GenericAPIView, DestroyModelMixin

UpdateAPIView
Used for update-only endpoints for a single model instance.

Provides put and patch method handlers.

Extends: GenericAPIView, UpdateModelMixin

ListCreateAPIView
Used for read-write endpoints to represent a collection of model instances.

Provides get and post method handlers.

Extends: GenericAPIView, ListModelMixin, CreateModelMixin

RetrieveUpdateAPIView
Used for read or update endpoints to represent a single model instance.

Provides get, put and patch method handlers.

Extends: GenericAPIView, RetrieveModelMixin, UpdateModelMixin

RetrieveDestroyAPIView
Used for read or delete endpoints to represent a single model instance.

Provides get and delete method handlers.

Extends: GenericAPIView, RetrieveModelMixin, DestroyModelMixin

RetrieveUpdateDestroyAPIView
Used for read-write-delete endpoints to represent a single model instance.

Provides get, put, patch and delete method handlers.

Extends: GenericAPIView, RetrieveModelMixin, UpdateModelMixin, DestroyModelMixin

Customizing the generic views
Often you'll want to use the existing generic views, but use some slightly customized behavior. If you find yourself reusing some bit of customized behavior in multiple places, you might want to refactor the behavior into a common class that you can then just apply to any view or viewset as needed.

Creating custom mixins
For example, if you need to lookup objects based on multiple fields in the URL conf, you could create a mixin class like the following:

class MultipleFieldLookupMixin(object):
"""
Apply this mixin to any view or viewset to get multiple field filtering
based on a lookup_fields attribute, instead of the default single field filtering.
"""
def get_object(self):
queryset = self.get_queryset() # Get the base queryset
queryset = self.filter_queryset(queryset) # Apply any filter backends
filter = {}
for field in self.lookup_fields:
if self.kwargs[field]: # Ignore empty fields.
filter[field] = self.kwargs[field]
obj = get_object_or_404(queryset, **filter) # Lookup the object
self.check_object_permissions(self.request, obj)
return obj
You can then simply apply this mixin to a view or viewset anytime you need to apply the custom behavior.

class RetrieveUserView(MultipleFieldLookupMixin, generics.RetrieveAPIView):
queryset = User.objects.all()
serializer_class = UserSerializer
lookup_fields = ['account', 'username']
Using custom mixins is a good option if you have custom behavior that needs to be used.

Creating custom base classes
If you are using a mixin across multiple views, you can take this a step further and create your own set of base views that can then be used throughout your project. For example:

class BaseRetrieveView(MultipleFieldLookupMixin,
generics.RetrieveAPIView):
pass

class BaseRetrieveUpdateDestroyView(MultipleFieldLookupMixin,
generics.RetrieveUpdateDestroyAPIView):
pass
Using custom base classes is a good option if you have custom behavior that consistently needs to be repeated across a large number of views throughout your project.

PUT as create
Prior to version 3.0 the REST framework mixins treated PUT as either an update or a create operation, depending on if the object already existed or not.

Allowing PUT as create operations is problematic, as it necessarily exposes information about the existence or non-existence of objects. It's also not obvious that transparently allowing re-creating of previously deleted instances is necessarily a better default behavior than simply returning 404 responses.

Both styles "PUT as 404" and "PUT as create" can be valid in different circumstances, but from version 3.0 onwards we now use 404 behavior as the default, due to it being simpler and more obvious.

If you need to generic PUT-as-create behavior you may want to include something like this AllowPUTAsCreateMixin class as a mixin to your views.

Third party packages
The following third party packages provide additional generic view implementations.

Django Rest Multiple Models
Django Rest Multiple Models provides a generic view (and mixin) for sending multiple serialized models and/or querysets via a single API request.