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DRF将数据传递到RelatedField

django-rest-framework django python

Eugene · 技术社区 · 6 年前

我有一个序列化程序和一个用于泛型外键关系的相关字段应该用来序列化 content_object 这是一个 ContentType 实例。我要检查一下 type 的 Notification 对象,我正在相关字段中序列化该对象,以便正确地知道要序列化到 data 参数在里面。实现这一目标的最佳方法是什么?

class NotificationRelatedField(serializers.RelatedField):

    def to_representation(self, value):
        data = {}
        # Need to check notification 'type' here
        return data


class NotificationRetrieveSerializer(serializers.ModelSerializer):
    content_object = NotificationRelatedField(read_only=True)

    class Meta:
        model = Notification
        fields = [
            'id',
            'created_at',
            'is_read',
            'type',
            'content_object',
        ]

2 回复 | 直到 6 年前

JPG 6 年前

可以使用 SerializerMethodField 作为,

class Content_Model_1_serializer(serializers.ModelSerializer):
    # you code
class Content_Model_2_serializer(serializers.ModelSerializer):
    # your code

class NotificationRetrieveSerializer(serializers.ModelSerializer):
    content_object = serializers.SerializerMethodField(read_only=True)

    def get_content_object(self, notification):
        if isinstance(notification.content_object, Content_Model_1):
            return Content_Model_1_serializer(notification.content_object).data
        if isinstance(notification.content_object, Content_Model_2):
            return Content_Model_2_serializer(notification.content_object).data
        ## and so on
        return None  # default case

    class Meta:
        model = Notification
        fields = [
            'id',
            'created_at',
            'is_read',
            'type',
            'content_object',
        ]

Content_Model_1 和 Content_Model_2 是由一般的FK关系和 Content_Model_1_serializer 和 Content_Model_2_serializer 是第三个序列化程序。

Sachin 6 年前

您需要重写序列化程序的 to_representation 方法调用字段的 代表 方法与 Notification 实例,而不是字段的值。

例子 :

class NotificationRetrieveSerializer(serializers.ModelSerializer):
    content_object = NotificationRelatedField(read_only=True)

    class Meta:
        model = Notification
        fields = [
            'id',
            'created_at',
            'is_read',
            'type',
            'content_object',
        ]

    # override to_representation method
    def to_representation(self, instance):
        # python3 for `super` call
        result = super().to_representation(instance)

        # python2 for `super` call
        # result = super(
        #     NotificationRetrieveSerializer, self
        # ).to_representatio(instance)

        # here you call your field's `to_representation` with current instance
        # as the argument rather than as the `value` of the field.
        result['content_object'] = content_object_field.to_representation(instance)

        return result

class NotificationRelatedField(serializers.RelatedField):

    # here `value` is now the `Notification` instance
    def to_representation(self, value):
        data = {}

        # get the type and this field's value
        type = value.type
        content_object = value.content_object

        return data