Question

当我尝试将商品添加到购物车中时，我正在创建一个电子商务，它会返回上述错误？

它在视图中抱怨这一行代码：

else:
   order.items.add(order_item)

查看

def add_to_cart(request, slug):
   item = get_object_or_404(Item, slug=slug)
   order_item = OrderItem.objects.get_or_create(
       item=item,
       user = request.user,
       ordered = False
   )
   order_qs = Order.objects.filter(user=request.user, ordered=False)
   if order_qs.exists():
       order = order_qs[0]
       #check if the order item is in the order
       if order.items.filter(item__slug=item.slug).exists():
           order_item.quantity += 1
           order_item.save()
       else:
           order.items.add(order_item)
   else:
       ordered_date = timezone.now()
       order = Order.objects.create(user=request.user, ordered_date=ordered_date)
       order.items.add(order_item)
   return redirect("core:product", slug=slug)

型号

class OrderItem(models.Model):
   user = models.ForeignKey(settings.AUTH_USER_MODEL,    on_delete=models.CASCADE)    
   ordered = models.BooleanField(default=False)
   item = models.ForeignKey(Item, on_delete=models.CASCADE)
   quantity = models.IntegerField(default=1) 



   def __str__(self):
       return f"{self.quantity} of {self.item.title}"

class Order(models.Model):
   user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
   items = models.ManyToManyField(OrderItem)
   start_date = models.DateTimeField(auto_now_add= True)
   ordered_date = models.DateTimeField()
   ordered = models.BooleanField(default=False)

   def __str__(self):
       return self.user.username

追踪

Internal Server Error: /add-to-cart/pants-2/
Traceback (most recent call last):
  File "/home/vince/Desktop/Dev-Projects/djangoEcommerce/django_project_boilerplate/env/lib/python3.6/site-packages/django/core/handlers/exception.py", line 34, in inner
    response = get_response(request)
  File "/home/vince/Desktop/Dev-Projects/djangoEcommerce/django_project_boilerplate/env/lib/python3.6/site-packages/django/core/handlers/base.py", line 115, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "/home/vince/Desktop/Dev-Projects/djangoEcommerce/django_project_boilerplate/env/lib/python3.6/site-packages/django/core/handlers/base.py", line 113, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/home/vince/Desktop/Dev-Projects/djangoEcommerce/django_project_boilerplate/core/views.py", line 38, in add_to_cart
    order.items.add(order_item)
  File "/home/vince/Desktop/Dev-Projects/djangoEcommerce/django_project_boilerplate/env/lib/python3.6/site-packages/django/db/models/fields/related_descriptors.py", line 965, in add
    through_defaults=through_defaults,
  File "/home/vince/Desktop/Dev-Projects/djangoEcommerce/django_project_boilerplate/env/lib/python3.6/site-packages/django/db/models/fields/related_descriptors.py", line 1092, in _add_items
    '%s__in' % target_field_name: new_ids,
  File "/home/vince/Desktop/Dev-Projects/djangoEcommerce/django_project_boilerplate/env/lib/python3.6/site-packages/django/db/models/query.py", line 892, in filter
    return self._filter_or_exclude(False, *args, **kwargs)
  File "/home/vince/Desktop/Dev-Projects/djangoEcommerce/django_project_boilerplate/env/lib/python3.6/site-packages/django/db/models/query.py", line 910, in _filter_or_exclude
    clone.query.add_q(Q(*args, **kwargs))
  File "/home/vince/Desktop/Dev-Projects/djangoEcommerce/django_project_boilerplate/env/lib/python3.6/site-packages/django/db/models/sql/query.py", line 1290, in add_q
    clause, _ = self._add_q(q_object, self.used_aliases)
  File "/home/vince/Desktop/Dev-Projects/djangoEcommerce/django_project_boilerplate/env/lib/python3.6/site-packages/django/db/models/sql/query.py", line 1318, in _add_q
    split_subq=split_subq, simple_col=simple_col,
  File "/home/vince/Desktop/Dev-Projects/djangoEcommerce/django_project_boilerplate/env/lib/python3.6/site-packages/django/db/models/sql/query.py", line 1251, in build_filter
    condition = self.build_lookup(lookups, col, value)
  File "/home/vince/Desktop/Dev-Projects/djangoEcommerce/django_project_boilerplate/env/lib/python3.6/site-packages/django/db/models/sql/query.py", line 1116, in build_lookup
    lookup = lookup_class(lhs, rhs)
  File "/home/vince/Desktop/Dev-Projects/djangoEcommerce/django_project_boilerplate/env/lib/python3.6/site-packages/django/db/models/lookups.py", line 20, in __init__
    self.rhs = self.get_prep_lookup()
  File "/home/vince/Desktop/Dev-Projects/djangoEcommerce/django_project_boilerplate/env/lib/python3.6/site-packages/django/db/models/fields/related_lookups.py", line 59, in get_prep_lookup
    self.rhs = [target_field.get_prep_value(v) for v in self.rhs]
  File "/home/vince/Desktop/Dev-Projects/djangoEcommerce/django_project_boilerplate/env/lib/python3.6/site-packages/django/db/models/fields/related_lookups.py", line 59, in <listcomp>
    self.rhs = [target_field.get_prep_value(v) for v in self.rhs]
  File "/home/vince/Desktop/Dev-Projects/djangoEcommerce/django_project_boilerplate/env/lib/python3.6/site-packages/django/db/models/fields/__init__.py", line 966, in get_prep_value
    return int(value)
TypeError: int() argument must be a string, a bytes-like object or a number, not 'OrderItem'
[24/Jun/2019 20:49:06] "GET /add-to-cart/pants-2/ HTTP/1.1" 500 150701

我需要它在购物车中创建一个新物品（如果它不存在），并且如果它存在于购物车中，它会将相似的物品增加1，而不是重新创建相同的物品。

Answer 1

Django get_or_create(..) [Django-doc]不会不返回模型实例，它返回带有对象的2元组和一个布尔值（无论是否创建记录）。或按照文档中的说明：

（..）

返回(object, created)的元组，其中object是   检索或创建的对象，并且created是一个布尔值，指定   是否创建了新对象。

（..）

您可以使用可迭代的拆包轻松解决此问题：

def add_to_cart(request, slug):
   item = get_object_or_404(Item, slug=slug)
   order_item, __ = OrderItem.objects.get_or_create(
       item=item,
       user = request.user,
       ordered = False
   )
   order_qs = Order.objects.filter(user=request.user, ordered=False)
   if order_qs.exists():
       order = order_qs[0]
       #check if the order item is in the order
       if order.items.filter(item__slug=item.slug).exists():
           order_item.quantity += 1
           order_item.save()
       else:
           order.items.add(order_item)
   else:
       ordered_date = timezone.now()
       order = Order.objects.create(user=request.user, ordered_date=ordered_date)
       order.items.add(order_item)
   return redirect("core:product", slug=slug)

因此，我们在此将OrderItem.objects.get_or_create(..)的结果分配给order_item, __，其中__是“丢弃变量”。

Answer 2

将以下行添加到此。只需添加“创建的”，如下所示。

 order_item, created = OrderItem.objects.get_or_create(
       item=item,
       user = request.user,
       ordered = False
   )

int（）参数必须是字符串，类似字节的对象或数字，而不是“ OrderItem”？ Django的

2 个答案: