每次创建父对象时创建外键对象的实例

Question

我想在我的数据库中创建一个链接到 User 模型的 Cart 对象。每次创建用户时，我都希望创建一个链接的购物车（在数据库中）。 有什么建议？我尝试将其链接到用户 ID，但没有任何乐趣。

models.py

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

# Create your models here.


class Product(models.Model):
    name = models.CharField(max_length=50)
    desc = models.CharField(max_length=50)
    img = models.FileField()
    created = models.DateField()
    num_stars = models.IntegerField()


class Cart(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE,to_field='id', null=True)
    content = models.CharField(max_length=50)
    last_update = models.DateTimeField()

Answer 1

只需在创建用户时让接收者处理购物车的创建

from django.dispatch import receiver
from django.db.models.signals import post_save
from django.contrib.auth.models import User
from django.utils import timezone
class Cart(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE,to_field='id', null=True)
    content = models.CharField(max_length=50,null=True,blank=True)
    last_update = models.DateTimeField(default=timezone.now)
@receiver(post_save, sender=User)
def create_user_cart(sender, instance, created, **kwargs):
    if created:
        Cart.objects.get_or_create(user=instance)