DRF

views.py：

# 自定义规则
class TestValidator(object):
    def __init__(self, base):
        self.base = base

    def __call__(self, value):
        # 规则明细
        if not value.startswith(self.base):
            message = "内容必须以 %s 为开头" % self.base
            raise serializers.ValidationError(message)

    def set_context(self, serializer_field):
        """
        This hook is called by the serializer instance,
        prior to the validation call being made.
        """
        # 执行验证之前调用，serializer_fields 是当前字段对象
        pass


class UserGroupSerializer(serializers.Serializer):
    title = serializers.CharField(
        error_messages={"blank": "内容不能为空"},
        validators=[TestValidator("AAAAA"),],  # 设置规则
    )


class UserGroupView(APIView):
    def post(self, request, *args, **kwargs):
        ser = UserGroupSerializer(data=request.data)
        if ser.is_valid():  # 如果 ser 有数据
            print(ser.validated_data["title"])
        else:
            print(ser.errors)  # 如果没数据，则打印错误信息
        return HttpResponse("ok")

提交不合规定的数据：