python - int() 参数必须是字符串、类似字节的对象或数字，而不是 'OrderItem' ？ Django

Question

我现在正在创建电子商务，当我尝试将商品添加到购物车时，它会返回上述错误吗？

它提示 View 中的这行代码:

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

回溯

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项目(如果它不存在)，如果它存在于购物车中，它会将相似的项目增加 1，而不是再次创建相同的项目。

Answer 1

Django get_or_create(..) [Django-doc] ，是否不返回模型实例，它返回带有对象的二元组和 bool 值(是否创建记录)。或者如文档中所写:

(..)

Returns a tuple of (object, created), where object is the retrieved or created object and created is a boolean specifying whether a new object was created.

(..)

但是，您可以通过使用可迭代解包轻松解决此问题:

def add_to_cart(request, slug):
   item = get_object_or_404(Item, slug=slug)
   <b>order_item, __</b> = 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)

在这里，我们将 OrderItem.objects.get_or_create(..) 的结果分配给 order_item, __，其中 __ 是一个“抛出”离开变量”。