通过浏览器访问端点时，CreateAPIView使用st（）函数返回TypeError

Question

我正在编写基于Django（2.2.2）和Django Rest Framework（3.9.4）的API。 目标是创建简单的消息系统。 创建用于创建消息的端点后，出现TypeError：

TypeError at /api/v1/message/create/
__str__ returned non-string (type Message)

The 'message_body' in the DB contains PL characteristic characters.

我为序列化器尝试了serializer.Serializer和serializer.ModelSerializer，为视图尝试了CreateAPIView和ListCreateAPIView。 真正有趣的是，用于列出消息的端点工作正常。

这几乎是我的其他终结点（也就是CreateAPIView）的复制粘贴代码，其工作正常。

我还在 str （自身）上尝试了一些编码方法，但猜测不正确。

sample.json ：（用于在浏览器中测试API的装置）

{
  "model": "core.message",
  "pk": 1,
  "fields": {
    "chat": 1,
    "message_body": "Wiadomość testowa 1",
    "sender": "user",
    "sent": "2019-05-05T10:20:37+01:00",
    "is_viewed": true
  }
}

models.py：

class Message(models.Model):
    """
    Model representing single message in DB
    """
    chat = models.ForeignKey(
        'Chat',
        on_delete=models.CASCADE,
        unique=False
    )
    message_body = models.TextField(blank=False, null=False)
    sender = models.CharField(max_length=4)
    sent = models.DateTimeField(auto_now_add=True)
    is_viewed = models.BooleanField(default=False)

    def __unicode__(self):
        return self.message_body

    def __str__(self):
        return self.message_body.decode('utf8')

views.py：

from rest_framework import generics, status
from rest_framework.authentication import TokenAuthentication
from rest_framework.permissions import IsAuthenticated
from rest_framework.response import Response
from message.serializers import (
    ListMessageSerializer,
    CreateMessageSerializer
)
from core.models import Message



class CreateMessageView(generics.CreateAPIView):
    """
    Create new message view
    """
    authentication_classes = (TokenAuthentication,)
    permission_classes = (IsAuthenticated,)
    serializer_class = CreateMessageSerializer

    def perform_create(self, serializer):
        """
        Save data to DB, if valid
        """
        if serializer.is_valid():
            serializer.save()
        else:
            return Response(
                serializer.errors,
                status.HTTP_400_BAD_REQUEST
            )

serializers.py

from rest_framework import serializers
from core.models import Chat, Message


class CreateMessageSerializer(serializers.ModelSerializer):
    """
    Serializer for creating ne message
    """

    class Meta:
        model = Message
        fields = (
            'id',
            'chat',
            'message_body',
            'sender',
            'sent',
            'is_viewed'
        )
        read_only_field = ('id',)

    def validate(self, attrs):
        """
        Validate request data
        """

        message_body = attrs.get('message_body')
        if not message_body or message_body is None:
            msg = _('Can\'t send empty message!')
            raise serializers.ValidationError(msg, code='authentication')

        return attrs

    def create(self, validated_data):
        """
        Insert Message into DB
        """

        return Message.objects.create(**validated_data)

url.py：

from django.urls import path
from message import views


app_name = 'message'
urlpatterns = [
    path('create/', views.CreateMessageView.as_view(), name='create'),
]

我希望能够在浏览器中打开以下视图： api / v1 / message / create / 并手动测试创建新消息：）

Answer 1

我删除了以下主键之间的重新关联： 聊天-DB中消息的父级

现在一切正常：）