Django: When I delete item from one of the user's shopping cart, that same item gets deleted from every user's shopping cart

Question

Using python 3.7

When I add item to the cart, the item gets added individually to each user, but I have delete button on the cart details page and the function in views.py looks like this:

def delete_cart_item(request, item_id):
    user_profile = get_object_or_404(User_Profile, user=request.user)
    shopping_cart = user_profile.shopping_cart_set.first()
    item = shopping_cart.items.get(pk=item_id)
    item.delete()
    return redirect('Sales:cart_details')

Those are my models:

class User_Profile(models.Model):
    user = models.OneToOneField(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)

class Item(models.Model):
    item_name = models.CharField(max_length=200)
    item_price = models.IntegerField()
    item_description = models.CharField(max_length=300)
    item_bought_price = models.IntegerField()
    stock_level = models.IntegerField()
    restock_level = models.IntegerField()

class Cart_Item(models.Model):
    item = models.OneToOneField(Item, on_delete=models.SET_NULL, null=True)


class Shopping_Cart(models.Model):
    ref_code = models.CharField(max_length=15)
    owner = models.ForeignKey(User_Profile, on_delete=models.SET_NULL, null=True)
    items = models.ManyToManyField(Cart_Item)

What is the issue here? I tried changing on_delete=models.SET_NULL of Cart_Item to on_delete=models.CASCADE but that didn't seem to change anything.

There also is a weird issue that when the cart is empty and I add the first item, that item cannot be deleted from the page, I can delete it from shell though.

Answer 1

You're deleting the actual item, rather than removing it from the many-to-many. You should do:

item = Item.objects.get(pk=item_id)
shopping_cart.items.remove(item)