DRF源码解析2--viewsets.ModelViewSet对视图的封装

DRF

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 2020/02/19   Share

viewsets

drf中 viewsets 对 view 进行了更加深层的封装,在CBV编程中减少代码的冗余,截取viewsets源码如下

class ModelViewSet(mixins.CreateModelMixin,
                   mixins.RetrieveModelMixin,
                   mixins.UpdateModelMixin,
                   mixins.DestroyModelMixin,
                   mixins.ListModelMixin,
                   GenericViewSet):
# 可以看到viewsets中的ModelViewSet只是继承了各种类,每一个类对应CBV的每一个方法,如CreateModelMixin则对应post方法
    pass

进入GenericViewSet的源码中,不难发现,GenericViewSet这个类主要是获取我们的数据和处理数据的组件

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class GenericViewSet(ViewSetMixin, generics.GenericAPIView):
    # GenericViewSet同样是继承了两个类
    pass

进入generics.GenericAPIView

class GenericAPIView(views.APIView):
   # queryset就是获取的ORM对象
    queryset = None
   # serializer_class是序列化的类
    serializer_class = None

    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就是和分页组件相关的类,默认为drf配置中的组件
    pagination_class = api_settings.DEFAULT_PAGINATION_CLASS

    def get_queryset(self):
		# 这里断言就是为了说明在继承这个类时,一定要有queryset属性或覆盖这个方法
        assert self.queryset is not None, (
            "'%s' should either include a `queryset` attribute, "
            "or override the `get_queryset()` method."
            % self.__class__.__name__
        )
		# 获取ORM对象
        queryset = self.queryset
        if isinstance(queryset, QuerySet):
            # Ensure queryset is re-evaluated on each request.
            queryset = queryset.all()
        return queryset

    def get_serializer(self, *args, **kwargs):
        serializer_class = self.get_serializer_class()
        kwargs['context'] = self.get_serializer_context()
		# serializer_class接收的参数可能不同
        return serializer_class(*args, **kwargs)

    def get_serializer_class(self):
		# 继承这个类时,一定要有serializer_classt属性或覆盖这个方法
        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):
        return {
            'request': self.request,
            'format': self.format_kwarg,
            'view': self
        }

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

接着回到ModelViewSet中,进入到mixins.CreateModelMixin的源码中

class CreateModelMixin:
    """
    Create a model instance.
    """
    def create(self, request, *args, **kwargs):
		# 这里调用的就是GenericAPIView中的get_serializer
        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 {}

现在我们只需要继承ModelViewSet,然后重写queryset和处理数据所需要的组件类如序列化的类等,但是怎么将self.post对应上self.list方法呢,GenericViewSet还继承了ViewSetMixin,看一下ViewSetMixin的源码的截取

class ViewSetMixin:
    @classonlymethod
	# 对as_view()方法又一次封装,action表示可以接收参数了
    def as_view(cls, actions=None, **initkwargs):
        if not actions:
            raise TypeError("The `actions` argument must be provided when "
                            "calling `.as_view()` on a ViewSet. For example "
                            "`.as_view({'get': 'list'})`")

        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
			# method, action退出action为一个字典,{'get':'list'}
            for method, action in actions.items():
				#  handler为实例中的各个方法
                handler = getattr(self, action)
				# 这里setattr相当于metmod == handler
                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)
        return csrf_exempt(view)

奉献一张图来看下我们的继承顺序

Author：liangweijiang

原文链接：https://liangweijiang.github.io/2020/02/19/DRF-02/

发表日期：February 19th 2020, 9:47:47 pm

更新日期：February 19th 2020, 11:08:42 pm

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1. viewsets
1. 1.0.1. 奉献一张图来看下我们的继承顺序

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