Django model_name.item.add(item) 将项目添加到模型中的所有记录

Question

我正在尝试使用 Django 实现电子商务网站的订单系统。我有 Order Model 和 OrderItem Model 这样的

class OrderItem(models.Model):
    product = models.ForeignKey(Product, on_delete=models.SET_NULL, null=True)
    is_ordered = models.BooleanField(default=False)
    owner = models.ForeignKey(User, on_delete=models.SET_NULL, null=True)
    date_added = models.DateTimeField(auto_now=True)
    date_ordered = models.DateTimeField(null = True)

    def __str__(self):
        return self.product.name

class Order(models.Model):
    ref_code = models.UUIDField(default=uuid.uuid4, editable=False)
    items = models.ManyToManyField(OrderItem)
    owner = models.ForeignKey(Profile, on_delete=models.SET_NULL, null=True)
    is_ordered = models.BooleanField(default=True)
    date_ordered = models.DateTimeField(auto_now=True)
    shipping = models.ForeignKey(AddressAndInfo, on_delete=models.SET_NULL, null=True)
    is_shipped = models.BooleanField(default=False)
    price = models.FloatField(default=0.0)

而我的视图函数是这样的：

def checkout(request):
order_items = OrderItem.objects.filter(
    owner=request.user).filter(is_ordered=False).all()

address = AddressAndInfo.objects.filter(user=request.user).get()
if(order_items.count() > 0):
    total = 0
    for item in OrderItem.objects.filter(owner=request.user).filter(is_ordered=False).all():
        if item.product.discounted_price > 0:
            total = total + item.product.discounted_price
        else:
            total = total + item.product.price
    order = Order.objects.create(
        owner = Profile.objects.get(user= request.user.id),
        shipping = address,
        price = total
    )
    new = Order.objects.get(items = None)
    print(new.ref_code)
    new.items.add(OrderItem.objects.get(owner=request.user, is_ordered=False))
    for item in order_items:
        item.is_ordered = True
        item.save()
    return redirect('dash')
else:
    messages.success(request, 'No item in Cart')
    return redirect('index')

现在的问题是，当我尝试从用户添加第二个订单时，它会将第二个订单中的订单项添加到所有现有订单中。结果是所有订单都有相同的订单项目。每当我尝试添加新订单时，新订单中的订单商品都会添加到所有现有订单中。

Answer 1

我用一些 cmets 对您的代码做了一些小改动，希望对您有所帮助！ :)

def checkout(request):
    order_items = OrderItem.objects.filter(owner=request.user, is_ordered=False).all()

    address = AddressAndInfo.objects.filter(user=request.user).get()
    if(order_items.count() > 0):
        total = 0
        # Look, you can reuse order_items here instead of making another query to the database :)
        for item in order_items:
            if item.product.discounted_price > 0:
                total = total + item.product.discounted_price
            else:
                total = total + item.product.price

        order = Order.objects.create(
            owner = Profile.objects.get(user= request.user.id),
            shipping = address,
            price = total
        )
        # I think you were making a request to the database to get the Order that has no items, 
        # are you sure it will be always be just one order?
        # Anyway that wouldn't be necessary if you already have the instance of the recently created order in the 'order' variable above
        # new = Order.objects.get(items = None)
        print(order.ref_code)

        # Just one item is being added to the recently created Order here, 
        # and another query is being made to the database to get just one OrderItem with (owner=request.user, is_ordered=False)
        # maybe the is_ordered value of the item would be modified after this but I think it's safer to add the item after changing that value
        # order.items.add(OrderItem.objects.get(owner=request.user, is_ordered=False))
        for item in order_items:
            item.is_ordered = True            
            item.save()
            # Instead each item should be added inside this loop after each one is modified and saved
            order.items.add(item)
        return redirect('dash')
    else:
        messages.success(request, 'No item in Cart')
        return redirect('index')

希望这能有所帮助！无论如何，我不确定您是否应该在Order 类中使用items = models.ManyToManyField(OrderItem)，因为您是说同一个ItemOrder 也可能属于许多Orders？而且我认为您想要做的是OrderItem 只能属于一个订单，对吗？也许您可以像这样在OrderItem 中添加一个“订单”ForeignKey 列：

class OrderItem(models.Model):
    product = models.ForeignKey(Product, on_delete=models.SET_NULL, null=True)
    order = models.ForeignKey(Order, on_delete=models.SET_NULL, null=True, related_name='items')
    is_ordered = models.BooleanField(default=False)
    owner = models.ForeignKey(User, on_delete=models.SET_NULL, null=True)
    date_added = models.DateTimeField(auto_now=True)
    date_ordered = models.DateTimeField(null = True)    

    def __str__(self):
        return self.product.name


class Order(models.Model):
    ref_code = models.UUIDField(default=uuid.uuid4, editable=False)
    owner = models.ForeignKey(Profile, on_delete=models.SET_NULL, null=True)
    is_ordered = models.BooleanField(default=True)
    date_ordered = models.DateTimeField(auto_now=True)
    shipping = models.ForeignKey(AddressAndInfo, on_delete=models.SET_NULL, null=True)
    is_shipped = models.BooleanField(default=False)
    price = models.FloatField(default=0.0)

如果您这样做，您所要做的就是在更新它们的最后一个循环中将订单分配给您的 OrderItems

for item in order_items:
    item.is_ordered = True 
    item.order = order          
    item.save()

现在您的 OrderItems 在数据库级别只有一个 Order :)