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，我得到 TypeError:

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

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

我为我的序列化程序尝试了 serializer.Serializer 和 serializer.ModelSerializer，为视图尝试了 CreateAPIView 和 ListCreateAPIView。 真正有趣的是，列出消息的端点工作得很好。

这几乎是来自我的另一个端点（也是 CreateAPIView）的复制粘贴代码，它按预期工作。

我也在 str(self) 上尝试了一些编码的东西，但猜测不正确。

sample.json：（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视图： api/v1/消息/创建/ 并测试手动创建新消息:)

Answer 1

我删除了 PrimaryKeys 之间的关系： 聊天 - DB 中消息的父级

现在一切正常:)