とValueError：「<通知：通知オブジェクトが>」この多対多の関係が

Question

を使用することができます前に、「通知」フィールドの値を持っている必要があり、私はこのモデルがあります、一方について

class Notification(BaseTimestampableModel): 
# TYPES CONSTANTS HERE 
# TYPE_CHOICES DICT HERE 

    sender = models.ForeignKey(User, related_name='sender_notifications') 
    receivers = models.ManyToManyField(User, related_name='receiver_notifications') 
    type = models.PositiveSmallIntegerField(choices=TYPE_CHOICES) 
    data = models.TextField() 
    sent = models.BooleanField(default=False) 

    class Meta: 
     verbose_name = _('Notification') 
     verbose_name_plural = _('Notifications') 


    def send(self): 
     # Logic for sending notification here 

     self.sent = True 
     self.save() 

を

ValueError: "<Notification: Notification object>" needs to have a value for field "notification" before this many-to-many relationship can be used. 

0：、私はこのエラーを取得する（メッセージとチャットがpreviusly保存されている）

class ChatNotifications: 
    @staticmethod 
    def message_created(message, chat): 
     """ 
     Send a notification when a chat message is created 
     to all users in chat except to the message's sender. 
     """ 
     sender = message.user 

     data = { 
      'text': message.text, 
      'phone': str(sender.phone_prefix) + str(sender.phone), 
      'chatid': chat.uuid.hex, 
      'time': timezone.now().timestamp(), 
      'type': 'text', 
      'msgid': message.uuid.hex 
     } 
     notification = Notification(
      sender=sender, 
      receivers=chat.get_other_users(sender), 
      type=Notification.TYPE_CHAT_MESSAGE, 
      data=json.dumps(data) 
     ) 
     notification.send() 

しかし、私はChatNotifications.message_createdを呼び出すとき（MSG、チャット）：私はこの "静的" クラスをしました

Googleで調べてみると、thisを試してみますが、これは私の問題を解決しません。

debugを使用すると、Modelコンストラクタが呼び出されたときにエラーがスローされていることを確認しました。

これはトレースです：

Traceback (most recent call last): 
File "<input>", line 1, in <module> 
File "/home/vagrant/petycash/apps/chats/notifications.py", line 45, in message_created 
data=json.dumps(data) 
File "/usr/local/lib/python3.5/dist-packages/django/db/models/base.py", line 550, in __init__ 
setattr(self, prop, kwargs[prop]) 
File "/usr/local/lib/python3.5/dist-packages/django/db/models/fields/related_descriptors.py", line 499, in __set__ 
manager = self.__get__(instance) 
File "/usr/local/lib/python3.5/dist-packages/django/db/models/fields/related_descriptors.py", line 476, in __get__ 
return self.related_manager_cls(instance) 
File "/usr/local/lib/python3.5/dist-packages/django/db/models/fields/related_descriptors.py", line 783, in __init__ 
(instance, self.source_field_name)) 
ValueError: "<Notification: Notification object>" needs to have a value for field "notification" before this many-to-many relationship can be used. 

Answer 1

それが保存されるまであなたがUserでNotificationを関連付けることはできません。

ですから、最初Notificationを保存する必要があり、あなたはreceivers

notification = Notification(
    sender=sender, 
    type=Notification.TYPE_CHAT_MESSAGE, 
    data=json.dumps(data) 
).save() 
# If chat.get_other_users(sender) return a queryset 
receivers = chat.get_other_users(sender) 
for receiver in receivers: 
    notification.receivers.add(receiver) 
# or you can also simply assign the whole list as it's already empty after new create 
# >>> notification.receivers = recievers 
notification.send()