Django restframework CBV一般继承特殊视图类的源码剖析及使用

class GenericAPIView(views.APIView):
    # 指定查询的数据集
    queryset = None
    # 指定序列化类
    serializer_class = None

    # If you want to use object lookups other than pk, set ‘lookup_field‘.
    # For more complex lookup requirements override `get_object()`.
    # 这两个变量在反向生成url会使用到
    lookup_field = ‘pk‘
    lookup_url_kwarg = None

    # 可以理解为查询的过滤条件
    filter_backends = api_settings.DEFAULT_FILTER_BACKENDS

    # 指定分页类
    pagination_class = api_settings.DEFAULT_PAGINATION_CLASS
    
    def get_queryset(self):
        # 这个方法是获取查询集
        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.
            # 这个就是查询集
            queryset = queryset.all()
        return queryset

    def get_object(self):
        # 这个方法就是根据过滤条件获取单个对象
        queryset = self.filter_queryset(self.get_queryset())

        # Perform the lookup filtering.
        # 返回其中的一个值，值的决定是基于下面式子终止的出口
        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)
        )

        # 根据参数以及参数的值去获取对象，如果没有就返回404页面
        filter_kwargs = {self.lookup_field: self.kwargs[lookup_url_kwarg]}
        obj = get_object_or_404(queryset, **filter_kwargs)

        # May raise a permission denied
        # 这个方法会跳转到权限验证类中，类中有一个方法就是has_object_permissions方法
        # 会验证当前对象是否有权限
        self.check_object_permissions(self.request, obj)

        return obj

    def get_serializer(self, *args, **kwargs):
        # 实例化序列化类对象
        serializer_class = self.get_serializer_class()
        # 将相关参数放置在context中
        kwargs[‘context‘] = self.get_serializer_context()
        return serializer_class(*args, **kwargs)

    def get_serializer_class(self):
        # 获取序列化类
        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
        }

    # 这个源码注释中提及方法不常用，就是根据条件获取单个查询对象
    def filter_queryset(self, queryset):
        for backend in list(self.filter_backends):
            queryset = backend().filter_queryset(self.request, queryset, self)
        return queryset
    
    @property
    def paginator(self):
        # 实例化分页类对象
        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):
        # 如果分页类对象为空，就返回空，否则就获取的数据集分页
        if self.paginator is None:
            return None
        return self.paginator.paginate_queryset(queryset, self.request, view=self)

    def get_paginated_response(self, data):
        # 这个方法就是额外显示上下一页url地址和总记录数
        assert self.paginator is not None
        return self.paginator.get_paginated_response(data)