您能解释一下我在这里提到的添加到购物车视图吗？

Question

我正在关注构建我的第一个电子商务应用程序的教程。我有点卡在他的“添加到购物车”视图中。

请帮助我在我不理解的视图中详细解释一些代码行。我将在要详细了解的代码行之前写“ Detail”一词。

首先是模型

User = get_user_model()

def looping():
    filename = item.name

class Item(models.Model):
    name   = models.CharField(max_length = 210)
    detail = models.TextField()
    more_detail = models.TextField(null=True)
    created = models.DateTimeField(auto_now_add =True)
    image  = models.ImageField(upload_to = "media/" +  time.strftime("%H-%m-%Y"),default = 'https://source.unsplash.com/random/232x266/')
    image2  = models.ImageField(upload_to = "media/" + time.strftime("%H-%m-%Y"),default = 'https://source.unsplash.com/random/232x267/')
    image3  = models.ImageField(upload_to = "media/" + time.strftime("%H-%m-%Y"),default = 'https://source.unsplash.com/random/232x266/')
    slug    = models.SlugField()

    def save(self, *args, **kwargs):
        self.slug = slugify(self.name)
        super().save(*args, **kwargs)


    def get_absolute_url(self):
        return reverse('item:detail',kwargs = {"slug":self.slug})



    initial_price = models.FloatField(null=True)
    price  = models.FloatField()

    CATEGORY_CHOICES = (

    ('Men','Men'),
    ('Women','Women'),
    ('Kids','Kids')

    )

    category = models.CharField(choices = CATEGORY_CHOICES,max_length = 210,default = "Men")


    label_CHOICES = (

    ('Hot','Hot'),
    ('Trending','Trending'),
    ('few','Few stocks left')

    )

    label = models.CharField(choices = label_CHOICES,max_length = 210,default = "Hot")



    def __str__(self):
        return self.name


class OrderItem(models.Model):
    user = models.ForeignKey(User,on_delete = models.CASCADE)
    item = models.ForeignKey(Item,default=False,null=True,blank=True,on_delete = models.CASCADE)

    def __str__(self):
        return self.item



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


    def __str__(self):
        return self.order

这是风景

def add_to_cart(request, slug):
    item = get_object_or_404(Item, slug=slug)

详细信息-如何创建带有ordered = False参数的order_item，因为它没有有序字段。该字段位于订单模型中

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

详细信息-为什么代码过滤订单，因为此视图是关于订单商品而不是订单

order_qs = Order.objects.filter（user = request.user，ordered = False）

    if order_qs.exists():
       order = order_qs[0]

详细信息-提示：为什么要过滤，该项目来自何处以及过滤器中的查询是什么，因为它在重复，所以我不知道

       if order.items.filter(item__slug=item.slug).exists():

详细信息---为什么我们要在这里增加数量

           order_item.quantity += 1
           order_item.save()
           messages.info(request, "This item quantity was updated.")
           return redirect("core:order-summary")
       else:

详细信息---为什么要添加它，因为它必须仅在卡中

           order.items.add(order_item)
           messages.info(request, "This item was added to your cart.")
           return redirect("core:order-summary")

详细信息-以及这方面写的内容为何创建订单并做不必要的事情

    else:
       ordered_date = timezone.now()
       order = Order.objects.create(
       user=request.user, ordered_date=ordered_date)
       order.items.add(order_item)
       messages.info(request, "This item was added to your cart.")
       return redirect("core:order-summary")