Django:禁止直接分配给多对多集的前端。使用user.set()代替 [英] Django : Direct assignment to the forward side of a many-to-many set is prohibited. Use user.set() instead
问题描述
当我尝试将当前登录的用户添加为 ManyToManyField
的另一个关系时,出现此错误。
I am getting this error when I try to add the current logged in user into another relation as ManyToManyField
.
TypeError: Direct assignment to the forward side of a many-to-many set is prohibited. Use user.set() instead.
这是我的代码:
Views.py
def add_to_cart(request , item):
name = item
size = request.POST.get("size")
extras = request.POST.get("extras")
c = Cart(item=name , size=size , extras=extras , user=request.user)
c.save()
return render(request , "orders/add_items.html" , {"message":f"{name} added to cart"})
Models.py
class Cart(models.Model):
item = models.CharField(max_length=64)
size = models.DecimalField(max_digits=5,decimal_places=2)
extras = models.CharField(max_length=64 , null=True, blank=True)
user = models.ManyToManyField(User , related_name="member")
def __str__(self):
return f"{item} added by {user}"
推荐答案
您需要先保存购物车,然后才能进行广告d个项目到多对多字段。
You need to save the cart before you can add items to the many-to-many field.
c = Cart(item=name , size=size , extras=extras)
c.save()
c.user.add(request.user)
保存后,您还可以使用 set()
。请注意,这将删除集合中未指定的所有相关用户(尽管在这种情况下,这是一个新列表,因此没有任何用户)。
You could also use set()
after saving. Note this will remove any related users not specified in the set (although in this case it's a new list so there aren't any).
c.user.set([request.user]
最后,确定要吗?一个多对多字段吗?这允许购物车属于多个用户。如果是这样,我将字段命名为 users
,而不是 user
。如果每个购物车只需要一个 user
,那么我将使用 ForeignKey
代替。您的related_name 成员
也没有意义,这用于获取与用户相关的购物车,所以我希望您使用 carts
。
Finally, are you sure you want a many-to-many field for this? That allows a cart to belong to multiple users. If that's the case, I would name the field users
, not user
. If you only want one user
per cart, then I would use a ForeignKey
instead. Your related_name members
doesn't make sense either. This is used to get the carts related to a user, so I would expect you to use carts
instead.
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