drf serializer获取viewset 中的上下文context,自定义上下文

1. 在视图继承ViewAPI时,在初始化序列化类时可以传递context参数

2. 在视图继承viewset后,我们只能对序列化类做一个声明,但是在实际创建序列化实例时,会帮我们将rquest参数传递到实列中,可以使用self.context来获取.

源码分析:

从BaseSerializer中:

class BaseSerializer(Field):
    """
    The BaseSerializer class provides a minimal class which may be used
    for writing custom serializer implementations.

    Note that we strongly restrict the ordering of operations/properties
    that may be used on the serializer in order to enforce correct usage.

    In particular, if a `data=` argument is passed then:

    .is_valid() - Available.
    .initial_data - Available.
    .validated_data - Only available after calling `is_valid()`
    .errors - Only available after calling `is_valid()`
    .data - Only available after calling `is_valid()`

    If a `data=` argument is not passed then:

    .is_valid() - Not available.
    .initial_data - Not available.
    .validated_data - Not available.
    .errors - Not available.
    .data - Available.
    """

    def __init__(self, instance=None, data=empty, **kwargs):
        self.instance = instance
        if data is not empty:
            self.initial_data = data
        self.partial = kwargs.pop('partial', False)
        self._context = kwargs.pop('context', {}) # 传递上下文参数
        kwargs.pop('many', None)
        super(BaseSerializer, self).__init__(**kwargs)

在viewset中是怎样自动传递上下文的的:

class GenericAPIView(views.APIView):
    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
      #这里设置了上下文
    def get_serializer_context(self):
        """
        Extra context provided to the serializer class.
        """
        return {
            'request': self.request,
            'format': self.format_kwarg,
            'view': self
        }

所以如果要自定以上下文的的值,可以重写get_serializer_context方法.