Django REST framework+Vue 打造生鲜超市（四）

# goods/view_base.py

from django.views.generic import View
from goods.models import Goods

class GoodsListView(View):
    def get(self,request):
        #通过django的view实现商品列表页
        json_list = []
        #获取所有商品
        goods = Goods.objects.all()
        for good in goods:
            json_dict = {}
            #获取商品的每个字段，键值对形式
            json_dict['name'] = good.name
            json_dict['category'] = good.category.name
            json_dict['market_price'] = good.market_price
            json_list.append(json_dict)

        from django.http import HttpResponse
        import json
        #返回json，一定要指定类型content_type='application/json'
        return HttpResponse(json.dumps(json_list),content_type='application/json')

from goods.view_base import GoodsListView

urlpatterns = [
   #商品列表页
    path('goods/',GoodsListView.as_view(),name='goods-list')
]

# goods/view_base.py

from django.views.generic import View
from goods.models import Goods

class GoodsListView(View):
    def get(self,request):
        #通过django的view实现商品列表页
        json_list = []
        #获取所有商品
        goods = Goods.objects.all()
        # for good in goods:
        #     json_dict = {}
        #     #获取商品的每个字段，键值对形式
        #     json_dict['name'] = good.name
        #     json_dict['category'] = good.category.name
        #     json_dict['market_price'] = good.market_price
        #     json_list.append(json_dict)

        from django.forms.models import model_to_dict
        for good in goods:
            json_dict = model_to_dict(good)
            json_list.append(json_dict)

        from django.http import HttpResponse
        import json
        #返回json，一定要指定类型content_type='application/json'
        return HttpResponse(json.dumps(json_list),content_type='application/json')

# goods/view_base.py

from django.views.generic import View
from goods.models import Goods

class GoodsListView(View):
    def get(self,request):
        #通过django的view实现商品列表页
        json_list = []
        #获取所有商品
        goods = Goods.objects.all()
        # for good in goods:
        #     json_dict = {}
        #     #获取商品的每个字段，键值对形式
        #     json_dict['name'] = good.name
        #     json_dict['category'] = good.category.name
        #     json_dict['market_price'] = good.market_price
        #     json_list.append(json_dict)

        import json
        from django.core import serializers
        from django.http import JsonResponse

        json_data = serializers.serialize('json',goods)
        json_data = json.loads(json_data)
        #In order to allow non-dict objects to be serialized set the safe parameter to False.
        return JsonResponse(json_data,safe=False)

from rest_framework.documentation import include_docs_urls

urlpatterns = [
    #drf文档，title自定义
    path('docs',include_docs_urls(title='仙剑奇侠传')),
]

INSTALLED_APPS = [
    'rest_framework',
]

urlpatterns = [
    path('api-auth/',include('rest_framework.urls')),
]

# goods/serializers.py

from rest_framework import serializers


class GoodsSerializer(serializers.Serializer):
    name = serializers.CharField(required=True,max_length=100)
    click_num = serializers.IntegerField(default=0)
    goods_front_image = serializers.ImageField()

# googd/views.py

from rest_framework.views import APIView
from goods.serializers import GoodsSerializer
from .models import Goods
from rest_framework.response import Response


class GoodsListView(APIView):
    '''
    商品列表
    '''
    def get(self,request,format=None):
        goods = Goods.objects.all()
        goods_serialzer = GoodsSerializer(goods,many=True)
        return Response(goods_serialzer.data)

# goods/serializers.py

from rest_framework import serializers
from .models import Goods

#Serializer实现商品列表页
# class GoodsSerializer(serializers.Serializer):
#     name = serializers.CharField(required=True,max_length=100)
#     click_num = serializers.IntegerField(default=0)
#     goods_front_image = serializers.ImageField()

#ModelSerializer实现商品列表页
class GoodsSerializer(serializers.ModelSerializer):
    class Meta:
        model = Goods
        fields = '__all__'

# goods/serializers.py

from rest_framework import serializers
from .models import Goods,GoodsCategory

#Serializer实现商品列表页
# class GoodsSerializer(serializers.Serializer):
#     name = serializers.CharField(required=True,max_length=100)
#     click_num = serializers.IntegerField(default=0)
#     goods_front_image = serializers.ImageField()


class CategorySerializer(serializers.ModelSerializer):
    class Meta:
        model = GoodsCategory
        fields = "__all__"


#ModelSerializer实现商品列表页
class GoodsSerializer(serializers.ModelSerializer):
    #覆盖外键字段
    category = CategorySerializer()
    class Meta:
        model = Goods
        fields = '__all__'

class GenericAPIView(views.APIView):
    """
    Base class for all other generic views.
    """
    # 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

    # If you want to use object lookups other than pk, set 'lookup_field'.
    # For more complex lookup requirements override `get_object()`.
    lookup_field = 'pk'
    lookup_url_kwarg = None

    # The filter backend classes to use for queryset filtering
    filter_backends = api_settings.DEFAULT_FILTER_BACKENDS

    # The style to use for queryset pagination.
    pagination_class = api_settings.DEFAULT_PAGINATION_CLASS

    def get_queryset(self):
        """
        Get the list of items for this view.
        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.

        (Eg. return a list of items that is specific to the user)
        """
        assert self.queryset is not None, (
            "'%s' should either include a `queryset` attribute, "
            "or override the `get_queryset()` method."
            % self.__class__.__name__
        )

        queryset = self.queryset
        if isinstance(queryset, QuerySet):
            # Ensure queryset is re-evaluated on each request.
            queryset = queryset.all()
        return queryset

    def get_object(self):
        """
        Returns the object the view is displaying.

        You may want to override this if you need to provide non-standard
        queryset lookups.  Eg if objects are referenced using multiple
        keyword arguments in the url conf.
        """
        queryset = self.filter_queryset(self.get_queryset())

        # Perform the lookup filtering.
        lookup_url_kwarg = self.lookup_url_kwarg or self.lookup_field

        assert lookup_url_kwarg in self.kwargs, (
            'Expected view %s to be called with a URL keyword argument '
            'named "%s". Fix your URL conf, or set the `.lookup_field` '
            'attribute on the view correctly.' %
            (self.__class__.__name__, lookup_url_kwarg)
        )

        filter_kwargs = {self.lookup_field: self.kwargs[lookup_url_kwarg]}
        obj = get_object_or_404(queryset, **filter_kwargs)

        # May raise a permission denied
        self.check_object_permissions(self.request, obj)

        return obj

    def get_serializer(self, *args, **kwargs):
        """
        Return the serializer instance that should be used for validating and
        deserializing input, and for serializing output.
        """
        serializer_class = self.get_serializer_class()
        kwargs['context'] = self.get_serializer_context()
        return serializer_class(*args, **kwargs)

    def get_serializer_class(self):
        """
        Return the class to use for the serializer.
        Defaults to using `self.serializer_class`.

        You may want to override this if you need to provide different
        serializations depending on the incoming request.

        (Eg. admins get full serialization, others get basic serialization)
        """
        assert self.serializer_class is not None, (
            "'%s' should either include a `serializer_class` attribute, "
            "or override the `get_serializer_class()` method."
            % self.__class__.__name__
        )

        return self.serializer_class

    def get_serializer_context(self):
        """
        Extra context provided to the serializer class.
        """
        return {
            'request': self.request,
            'format': self.format_kwarg,
            'view': self
        }

    def filter_queryset(self, queryset):
        """
        Given a queryset, filter it with whichever filter backend is in use.

        You are unlikely to want to override this method, although you may need
        to call it either from a list view, or from a custom `get_object`
        method if you want to apply the configured filtering backend to the
        default queryset.
        """
        for backend in list(self.filter_backends):
            queryset = backend().filter_queryset(self.request, queryset, self)
        return queryset

    @property
    def paginator(self):
        """
        The paginator instance associated with the view, or `None`.
        """
        if not hasattr(self, '_paginator'):
            if self.pagination_class is None:
                self._paginator = None
            else:
                self._paginator = self.pagination_class()
        return self._paginator

    def paginate_queryset(self, queryset):
        """
        Return a single page of results, or `None` if pagination is disabled.
        """
        if self.paginator is None:
            return None
        return self.paginator.paginate_queryset(queryset, self.request, view=self)

    def get_paginated_response(self, data):
        """
        Return a paginated style `Response` object for the given output data.
        """
        assert self.paginator is not None
        return self.paginator.get_paginated_response(data)

用的时候需要定义queryset和serializer_class
GenericAPIView里面默认为空

class ListModelMixin(object):
    """
    List a queryset.
    """
    def list(self, request, *args, **kwargs):
        queryset = self.filter_queryset(self.get_queryset())

        page = self.paginate_queryset(queryset)
        if page is not None:
            serializer = self.get_serializer(page, many=True)
            return self.get_paginated_response(serializer.data)

        serializer = self.get_serializer(queryset, many=True)
        return Response(serializer.data)

from goods.serializers import GoodsSerializer
from .models import Goods
from rest_framework.response import Response
from rest_framework import mixins
from rest_framework import generics


class GoodsListView(mixins.ListModelMixin,generics.GenericAPIView):
    '商品列表页'
    queryset = Goods.objects.all()
    serializer_class = GoodsSerializer

    def get(self,request,*args,**kwargs):
        return self.list(request,*args,**kwargs)

class GoodsListView(generics.ListAPIView):
    '商品列表页'
    queryset = Goods.objects.all()
    serializer_class = GoodsSerializer

"""
Settings for REST framework are all namespaced in the REST_FRAMEWORK setting.
For example your project's `settings.py` file might look like this:

REST_FRAMEWORK = {
    'DEFAULT_RENDERER_CLASSES': (
        'rest_framework.renderers.JSONRenderer',
        'rest_framework.renderers.TemplateHTMLRenderer',
    )
    'DEFAULT_PARSER_CLASSES': (
        'rest_framework.parsers.JSONParser',
        'rest_framework.parsers.FormParser',
        'rest_framework.parsers.MultiPartParser'
    )
}

This module provides the `api_setting` object, that is used to access
REST framework settings, checking for user settings first, then falling
back to the defaults.
"""
from __future__ import unicode_literals

from importlib import import_module

from django.conf import settings
from django.test.signals import setting_changed
from django.utils import six

from rest_framework import ISO_8601

DEFAULTS = {
    # Base API policies
    'DEFAULT_RENDERER_CLASSES': (
        'rest_framework.renderers.JSONRenderer',
        'rest_framework.renderers.BrowsableAPIRenderer',
    ),
    'DEFAULT_PARSER_CLASSES': (
        'rest_framework.parsers.JSONParser',
        'rest_framework.parsers.FormParser',
        'rest_framework.parsers.MultiPartParser'
    ),
    'DEFAULT_AUTHENTICATION_CLASSES': (
        'rest_framework.authentication.SessionAuthentication',
        'rest_framework.authentication.BasicAuthentication'
    ),
    'DEFAULT_PERMISSION_CLASSES': (
        'rest_framework.permissions.AllowAny',
    ),
    'DEFAULT_THROTTLE_CLASSES': (),
    'DEFAULT_CONTENT_NEGOTIATION_CLASS': 'rest_framework.negotiation.DefaultContentNegotiation',
    'DEFAULT_METADATA_CLASS': 'rest_framework.metadata.SimpleMetadata',
    'DEFAULT_VERSIONING_CLASS': None,

    # Generic view behavior
    'DEFAULT_PAGINATION_CLASS': None,
    'DEFAULT_FILTER_BACKENDS': (),

    # Schema
    'DEFAULT_SCHEMA_CLASS': 'rest_framework.schemas.AutoSchema',

    # Throttling
    'DEFAULT_THROTTLE_RATES': {
        'user': None,
        'anon': None,
    },
    'NUM_PROXIES': None,

    # Pagination
    'PAGE_SIZE': None,

    # Filtering
    'SEARCH_PARAM': 'search',
    'ORDERING_PARAM': 'ordering',

    # Versioning
    'DEFAULT_VERSION': None,
    'ALLOWED_VERSIONS': None,
    'VERSION_PARAM': 'version',

    # Authentication
    'UNAUTHENTICATED_USER': 'django.contrib.auth.models.AnonymousUser',
    'UNAUTHENTICATED_TOKEN': None,

    # View configuration
    'VIEW_NAME_FUNCTION': 'rest_framework.views.get_view_name',
    'VIEW_DESCRIPTION_FUNCTION': 'rest_framework.views.get_view_description',

    # Exception handling
    'EXCEPTION_HANDLER': 'rest_framework.views.exception_handler',
    'NON_FIELD_ERRORS_KEY': 'non_field_errors',

    # Testing
    'TEST_REQUEST_RENDERER_CLASSES': (
        'rest_framework.renderers.MultiPartRenderer',
        'rest_framework.renderers.JSONRenderer'
    ),
    'TEST_REQUEST_DEFAULT_FORMAT': 'multipart',

    # Hyperlink settings
    'URL_FORMAT_OVERRIDE': 'format',
    'FORMAT_SUFFIX_KWARG': 'format',
    'URL_FIELD_NAME': 'url',

    # Input and output formats
    'DATE_FORMAT': ISO_8601,
    'DATE_INPUT_FORMATS': (ISO_8601,),

    'DATETIME_FORMAT': ISO_8601,
    'DATETIME_INPUT_FORMATS': (ISO_8601,),

    'TIME_FORMAT': ISO_8601,
    'TIME_INPUT_FORMATS': (ISO_8601,),

    # Encoding
    'UNICODE_JSON': True,
    'COMPACT_JSON': True,
    'STRICT_JSON': True,
    'COERCE_DECIMAL_TO_STRING': True,
    'UPLOADED_FILES_USE_URL': True,

    # Browseable API
    'HTML_SELECT_CUTOFF': 1000,
    'HTML_SELECT_CUTOFF_TEXT': "More than {count} items...",

    # Schemas
    'SCHEMA_COERCE_PATH_PK': True,
    'SCHEMA_COERCE_METHOD_NAMES': {
        'retrieve': 'read',
        'destroy': 'delete'
    },
}


# List of settings that may be in string import notation.
IMPORT_STRINGS = (
    'DEFAULT_RENDERER_CLASSES',
    'DEFAULT_PARSER_CLASSES',
    'DEFAULT_AUTHENTICATION_CLASSES',
    'DEFAULT_PERMISSION_CLASSES',
    'DEFAULT_THROTTLE_CLASSES',
    'DEFAULT_CONTENT_NEGOTIATION_CLASS',
    'DEFAULT_METADATA_CLASS',
    'DEFAULT_VERSIONING_CLASS',
    'DEFAULT_PAGINATION_CLASS',
    'DEFAULT_FILTER_BACKENDS',
    'DEFAULT_SCHEMA_CLASS',
    'EXCEPTION_HANDLER',
    'TEST_REQUEST_RENDERER_CLASSES',
    'UNAUTHENTICATED_USER',
    'UNAUTHENTICATED_TOKEN',
    'VIEW_NAME_FUNCTION',
    'VIEW_DESCRIPTION_FUNCTION'
)


# List of settings that have been removed
REMOVED_SETTINGS = (
    "PAGINATE_BY", "PAGINATE_BY_PARAM", "MAX_PAGINATE_BY",
)


def perform_import(val, setting_name):
    """
    If the given setting is a string import notation,
    then perform the necessary import or imports.
    """
    if val is None:
        return None
    elif isinstance(val, six.string_types):
        return import_from_string(val, setting_name)
    elif isinstance(val, (list, tuple)):
        return [import_from_string(item, setting_name) for item in val]
    return val


def import_from_string(val, setting_name):
    """
    Attempt to import a class from a string representation.
    """
    try:
        # Nod to tastypie's use of importlib.
        module_path, class_name = val.rsplit('.', 1)
        module = import_module(module_path)
        return getattr(module, class_name)
    except (ImportError, AttributeError) as e:
        msg = "Could not import '%s' for API setting '%s'. %s: %s." % (val, setting_name, e.__class__.__name__, e)
        raise ImportError(msg)


class APISettings(object):
    """
    A settings object, that allows API settings to be accessed as properties.
    For example:

        from rest_framework.settings import api_settings
        print(api_settings.DEFAULT_RENDERER_CLASSES)

    Any setting with string import paths will be automatically resolved
    and return the class, rather than the string literal.
    """
    def __init__(self, user_settings=None, defaults=None, import_strings=None):
        if user_settings:
            self._user_settings = self.__check_user_settings(user_settings)
        self.defaults = defaults or DEFAULTS
        self.import_strings = import_strings or IMPORT_STRINGS
        self._cached_attrs = set()

    @property
    def user_settings(self):
        if not hasattr(self, '_user_settings'):
            self._user_settings = getattr(settings, 'REST_FRAMEWORK', {})
        return self._user_settings

    def __getattr__(self, attr):
        if attr not in self.defaults:
            raise AttributeError("Invalid API setting: '%s'" % attr)

        try:
            # Check if present in user settings
            val = self.user_settings[attr]
        except KeyError:
            # Fall back to defaults
            val = self.defaults[attr]

        # Coerce import strings into classes
        if attr in self.import_strings:
            val = perform_import(val, attr)

        # Cache the result
        self._cached_attrs.add(attr)
        setattr(self, attr, val)
        return val

    def __check_user_settings(self, user_settings):
        SETTINGS_DOC = "http://www.django-rest-framework.org/api-guide/settings/"
        for setting in REMOVED_SETTINGS:
            if setting in user_settings:
                raise RuntimeError("The '%s' setting has been removed. Please refer to '%s' for available settings." % (setting, SETTINGS_DOC))
        return user_settings

    def reload(self):
        for attr in self._cached_attrs:
            delattr(self, attr)
        self._cached_attrs.clear()
        if hasattr(self, '_user_settings'):
            delattr(self, '_user_settings')


api_settings = APISettings(None, DEFAULTS, IMPORT_STRINGS)


def reload_api_settings(*args, **kwargs):
    setting = kwargs['setting']
    if setting == 'REST_FRAMEWORK':
        api_settings.reload()


setting_changed.connect(reload_api_settings)

REST_FRAMEWORK = {
    #分页
    'DEFAULT_PAGINATION_CLASS': 'rest_framework.pagination.PageNumberPagination',
    #每页显示的个数
    'PAGE_SIZE': 10,
}

from rest_framework.pagination import PageNumberPagination

class GoodsPagination(PageNumberPagination):
    '''
    商品列表自定义分页
    '''
    #默认每页显示的个数
    page_size = 10
    #可以动态改变每页显示的个数
    page_size_query_param = 'page_size'
    #页码参数
    page_query_param = 'page'
    #最多能显示多少页
    max_page_size = 100


class GoodsListView(generics.ListAPIView):
    '商品列表页'

    pagination_class = GoodsPagination    #分页
    queryset = Goods.objects.all()
    serializer_class = GoodsSerializer

class ViewSetMixin(object):
    """
    This is the magic.

    Overrides `.as_view()` so that it takes an `actions` keyword that performs
    the binding of HTTP methods to actions on the Resource.

    For example, to create a concrete view binding the 'GET' and 'POST' methods
    to the 'list' and 'create' actions...

    view = MyViewSet.as_view({'get': 'list', 'post': 'create'})
    """

    @classonlymethod
    def as_view(cls, actions=None, **initkwargs):
        """
        Because of the way class based views create a closure around the
        instantiated view, we need to totally reimplement `.as_view`,
        and slightly modify the view function that is created and returned.
        """
        # The suffix initkwarg is reserved for displaying the viewset type.
        # eg. 'List' or 'Instance'.
        cls.suffix = None

        # The detail initkwarg is reserved for introspecting the viewset type.
        cls.detail = None

        # Setting a basename allows a view to reverse its action urls. This
        # value is provided by the router through the initkwargs.
        cls.basename = None

        # actions must not be empty
        if not actions:
            raise TypeError("The `actions` argument must be provided when "
                            "calling `.as_view()` on a ViewSet. For example "
                            "`.as_view({'get': 'list'})`")

        # sanitize keyword arguments
        for key in initkwargs:
            if key in cls.http_method_names:
                raise TypeError("You tried to pass in the %s method name as a "
                                "keyword argument to %s(). Don't do that."
                                % (key, cls.__name__))
            if not hasattr(cls, key):
                raise TypeError("%s() received an invalid keyword %r" % (
                    cls.__name__, key))

        def view(request, *args, **kwargs):
            self = cls(**initkwargs)
            # We also store the mapping of request methods to actions,
            # so that we can later set the action attribute.
            # eg. `self.action = 'list'` on an incoming GET request.
            self.action_map = actions

            # Bind methods to actions
            # This is the bit that's different to a standard view
            for method, action in actions.items():
                handler = getattr(self, action)
                setattr(self, method, handler)

            if hasattr(self, 'get') and not hasattr(self, 'head'):
                self.head = self.get

            self.request = request
            self.args = args
            self.kwargs = kwargs

            # And continue as usual
            return self.dispatch(request, *args, **kwargs)

        # take name and docstring from class
        update_wrapper(view, cls, updated=())

        # and possible attributes set by decorators
        # like csrf_exempt from dispatch
        update_wrapper(view, cls.dispatch, assigned=())

        # We need to set these on the view function, so that breadcrumb
        # generation can pick out these bits of information from a
        # resolved URL.
        view.cls = cls
        view.initkwargs = initkwargs
        view.suffix = initkwargs.get('suffix', None)
        view.actions = actions
        return csrf_exempt(view)

    def initialize_request(self, request, *args, **kwargs):
        """
        Set the `.action` attribute on the view, depending on the request method.
        """
        request = super(ViewSetMixin, self).initialize_request(request, *args, **kwargs)
        method = request.method.lower()
        if method == 'options':
            # This is a special case as we always provide handling for the
            # options method in the base `View` class.
            # Unlike the other explicitly defined actions, 'metadata' is implicit.
            self.action = 'metadata'
        else:
            self.action = self.action_map.get(method)
        return request

    def reverse_action(self, url_name, *args, **kwargs):
        """
        Reverse the action for the given `url_name`.
        """
        url_name = '%s-%s' % (self.basename, url_name)
        kwargs.setdefault('request', self.request)

        return reverse(url_name, *args, **kwargs)

    @classmethod
    def get_extra_actions(cls):
        """
        Get the methods that are marked as an extra ViewSet `@action`.
        """
        return [method for _, method in getmembers(cls, _is_extra_action)]

from goods.views import GoodsListViewSet
from rest_framework.routers import DefaultRouter

router = DefaultRouter()

#配置goods的url
router.register(r'goods', GoodsListViewSet)

urlpatterns = [
    #商品列表页
    re_path('^', include(router.urls)),
]

class GoodsListViewSet(mixins.ListModelMixin,viewsets.GenericViewSet):
    '商品列表页'

    # 分页
    pagination_class = GoodsPagination
    #这里必须要定义一个默认的排序,否则会报错
    queryset = Goods.objects.all().order_by('id')
    serializer_class = GoodsSerializer

"""
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 rest_framework import status
from rest_framework.response import Response
from rest_framework.settings import api_settings


class CreateModelMixin(object):
    """
    Create a model instance.
    """
    def create(self, request, *args, **kwargs):
        serializer = self.get_serializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        self.perform_create(serializer)
        headers = self.get_success_headers(serializer.data)
        return Response(serializer.data, status=status.HTTP_201_CREATED, headers=headers)

    def perform_create(self, serializer):
        serializer.save()

    def get_success_headers(self, data):
        try:
            return {'Location': str(data[api_settings.URL_FIELD_NAME])}
        except (TypeError, KeyError):
            return {}


class ListModelMixin(object):
    """
    List a queryset.
    """
    def list(self, request, *args, **kwargs):
        queryset = self.filter_queryset(self.get_queryset())

        page = self.paginate_queryset(queryset)
        if page is not None:
            serializer = self.get_serializer(page, many=True)
            return self.get_paginated_response(serializer.data)

        serializer = self.get_serializer(queryset, many=True)
        return Response(serializer.data)


class RetrieveModelMixin(object):
    """
    Retrieve a model instance.
    """
    def retrieve(self, request, *args, **kwargs):
        instance = self.get_object()
        serializer = self.get_serializer(instance)
        return Response(serializer.data)


class UpdateModelMixin(object):
    """
    Update a model instance.
    """
    def update(self, request, *args, **kwargs):
        partial = kwargs.pop('partial', False)
        instance = self.get_object()
        serializer = self.get_serializer(instance, data=request.data, partial=partial)
        serializer.is_valid(raise_exception=True)
        self.perform_update(serializer)

        if getattr(instance, '_prefetched_objects_cache', None):
            # If 'prefetch_related' has been applied to a queryset, we need to
            # forcibly invalidate the prefetch cache on the instance.
            instance._prefetched_objects_cache = {}

        return Response(serializer.data)

    def perform_update(self, serializer):
        serializer.save()

    def partial_update(self, request, *args, **kwargs):
        kwargs['partial'] = True
        return self.update(request, *args, **kwargs)


class DestroyModelMixin(object):
    """
    Destroy a model instance.
    """
    def destroy(self, request, *args, **kwargs):
        instance = self.get_object()
        self.perform_destroy(instance)
        return Response(status=status.HTTP_204_NO_CONTENT)

    def perform_destroy(self, instance):
        instance.delete()