在创建模型时创建OneToOne实例 [英] Create OneToOne instance on model creation

问题描述

我正在构建我的第一个django应用程序。我有一个用户，用户有一个收藏夹列表。用户只有一个收藏夹列表，该列表专属于该用户。

  class User（models.Model）： 
 name = models.CharField（max_length = 200）
 
 class FavouriteList（models.Model）：
 user = models.OneToOneField（User）
 favorites = models。 ManyToManyField（Favorite，blank = True）
  

当创建新用户时，我想确保用户有一个 FavouriteList 。有没有人知道如何确保一个模型有一个子对象（例如<$ code> FavouriteList ）当创建它时

解决方案

是使用Django信号系统。您可以将用户模型的post_save信号附加一个信号处理程序（只是某个功能），并在该回调内创建收藏列表。

 从django.db.models.signals导入post_save 
从django.dispatch导入接收器
从django.contrib.auth.models导入用户
 
 @receiver（ post_save，sender = User）
 def create_favorites（发件人，实例，创建，** kwargs）：
如果创建：
 Favorites.objects.create（user = instance）
  

以上是从 Django signal docs 。请务必仔细阅读信号文档，因为有几个问题可以阻止您，例如您的信号处理程序代码应该在哪里生活，以及如何避免重复的处理程序。

I'm building my first django app. I have a user, and the user has a list of favourites. A user has exactly one list of favourites, and that list belongs exclusively to that user.

class User(models.Model):
    name = models.CharField(max_length=200)

class FavouriteList(models.Model):
    user = models.OneToOneField(User)
    favourites = models.ManyToManyField(Favourite, blank=True)

When a new user is created, I want to ensure that the user has a FavouriteList. I've looked around in the Django documentation and haven't had much luck.

Does anyone know how I can ensure that a model has a child object (e.g. FavouriteList) when it is created?

解决方案

The most common way to accomplish this is to use the Django signals system. You can attach a signal handler (just a function somewhere) to the post_save signal for the User model, and create your favorites list inside of that callback.

from django.db.models.signals import post_save
from django.dispatch import receiver
from django.contrib.auth.models import User

@receiver(post_save, sender=User)
def create_favorites(sender, instance, created, **kwargs):
    if created:
        Favorites.objects.create(user=instance)

The above was adapted from the Django signals docs. Be sure to read the signals docs entirely because there are a few issues that can snag you such as where your signal handler code should live and how to avoid duplicate handlers.

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