Question

我想限制可以添加到购物车的产品数量。

--案例场景：假设交付资源稀缺，我不希望用户一次添加超过 5 个产品。（但同种产品的数量可以增加）

cart-app/cart.py

def add(self, product, quantity=1, override_quantity=False):
    product_id = str(product.id)
    if product_id not in self.cart:
        self.cart[product_id] = {'quantity': 0, 'price': str(product.price)}
    if override_quantity:
        self.cart[product_id]['quantity'] = quantity
    else:
        self.cart[product_id]['quantity'] += quantity
    self.save()

def __iter__(self):
    products = Product.objects.filter(id__in=product_ids)
    cart = self.cart.copy()

    for product in products:
        cart[str(product.id)]['product'] = product

    for item in cart.values():
        item['price'] = Decimal(item['price'])
        item['total_price'] = item['price'] * item['quantity']
        yield item

我试过对查询进行切片，但这不起作用。有什么想法吗？

Answer 1

当 product_id 尚未在购物车中并且购物车已有五件（或更多）商品时，您可以引发错误：

def add(self, product, quantity=1, override_quantity=False):
    product_id = str(product.id)
    if product_id not in self.cart and len(self.cart) >= 5:
        raise ValueError('Can not add more products to the cart')
    # …

在您的视图中，您可以尝试将商品添加到购物车，如果没有，则返回 HTTP 响应：

from django.http import HttpResponse

def my_view(request):
    # …
    try:
        cart.add(product)
    except ValueError:
        return HttpResponse('Can not add to the cart', status=400)
    # …

Answer 2

您需要在添加更多商品之前检查数量。

def add(self, product, quantity=1, override_quantity=False):
    product_id = str(product.id)

    if override_quantity:
        self.cart[product_id]['quantity'] = quantity
    else:
        self.cart[product_id]['quantity'] += quantity
    try:
        if product_id not in self.cart and self.cart[product_id]['quantity'] >= 5:
            self.cart[product_id] = {'quantity': 0, 'price': str(product.price)}
        else:
            print("You can not add more than 5 items.")
    except KeyError:
        print("quantity key is unknown.")
    self.save()

购物车产品数量限制

2 个答案: