python - Django url 不带参数

Question

我真的很难理解将参数和关键字参数分派(dispatch)给 Django url 的方法。以下为案例分析:

我有一个使用通用基本 View 的 View :

class CartView(View):
   def get(self, request, *args, **kwargs):
       item = request.GET.get('item')
       qty = request.GET.get('qty')
       print item, qty
       return HttpResponseRedirect('/')

通过上面的 View ，我能够使用像 "localhost:8000/cart/?item=4&qty=200" 这样的 url 中的参数，并在终端中打印带有数量的项目。

一旦我对代码进行了更改，例如:

from carts.models import Cart, CartItem
from products.models import Variation


class CartView(View):
    def get(self, request, *args, **kwargs):
        item_id = request.GET.get('item')
        if item_id:
            item_instance = get_object_or_404(Variation, id=item_id)
            qty = request.GET.get('qty')
            cart = Cart.objects.all()[0]
            cart_item = CartItem.objects.get_or_create(cart=cart, item=item_instance)[0]
            cart_item.quantity = qty
            cart_item.save()
            print cart_item
        return HttpResponseRedirect('/')

以相同的方式传递诸如 "localhost:8000/cart/?item=4&qty=200" 之类的参数，它会向我显示错误:

404 Page Not Found No Variation matches the given query.

url.py

urlpatterns = [
    url(r'^home/$', 'newsletter.views.home', name='home'),
    url(r'^contact/$', 'newsletter.views.contact', name='contact'),
    url(r'^about/$', 'project.views.about', name='about'),
    url(r'^admin/', include(admin.site.urls)),
    url(r'^accounts/', include('registration.backends.default.urls')),
    url(r'^cart/$', CartView.as_view(), name='cart'),
    url(r'^', include('products.urls')),
    url(r'^categories/', include('products.urls_categories')),

Answer 1

404 Page Not Found

No Variation matches the given query.

此消息来自您的线路:

item_instance = get_object_or_404(Variation, id=item_id)

并且意味着您没有与给定 id 匹配的 Variation 对象。