我想覆盖保存方法以便
- 如果cart_item已经存在，则更新数量
- 如果cart_item不存在，则插入新条目
但每次保存方法后，它都会陷入无限循环
class Cart(models.Model):
id = models.UUIDField(primary_key=True, default=uuid4)
created_at = models.DateTimeField(auto_now_add=True)
updated_at = models.DateTimeField(auto_now=True)
def __str__(self) -> str:
return str(self.id)
class CartItem(models.Model):
cart = models.ForeignKey(Cart, on_delete=models.CASCADE, related_name='items')
product = models.ForeignKey(Product, on_delete=models.CASCADE)
quantity = models.PositiveIntegerField()
def __str__(self) -> str:
return self.product.name
def save(self, *args, **kwargs):
try:
cart_item = CartItem.objects.get(cart_id=self.cart.id, product_id=self.product.id)
cart_item.quantity += self.quantity
pprint(cart_item)
cart_item.save() #after this line goes into infinite loop
except CartItem.DoesNotExist:
super().save(*args, **kwargs) #after this line goes into infinite loop
pprint("-------------------------here")
``
def save(self, *args, **kwargs):
if self._state.adding:
try:
cart_item = CartItem.objects.get(cart_id=self.cart.id, product_id=self.product.id)
quantity = cart_item.quantity + self.quantity
CartItem.objects.filter(pk=cart_item.id).update(quantity=quantity)
except CartItem.DoesNotExist:
super(CartItem, self).save(*args, **kwargs)
else:
super(CartItem, self).save(*args, **kwargs)
使用上面的代码，我可以实现我想要的。Save((函数同时用于插入和更新，我只想改变插入行为，所以为了检查正在执行的操作，我从这个页面获得了帮助。如果我使用模型的update((方法进行更新，它不会进入无限循环