Django：字符串对象打印出 None

Question

您好，我有一个删除订单号的视图。删除字符串后，网页会重定向到客户端页面，让用户知道订单号已删除。有问题。我明白了。

上一个订单未删除

它显示无，但我希望它注明我已删除的订单号。似乎没有显示，因为我已经删除了该订单号，所以当它在订单号列表中查找时，找不到该号码。

编辑：这是解决方案。订单号应在消息发送后删除。

   def delete_confirmation(request, order_no = 0, service_type = 0):
        order = None
        count = 0
        title = models.SERVICE_CHOICES[int(service_type) - 1][1]
        #title = type[1]
        order_number = request.session['order_number']
        try:
            order = models.Order.objects.get(pk = order_no)
            count = order.orderservicelist_set.count()
            if request.POST.get('delete'):
                request.user.message_set.create(message = "Previous order " + str(order_number.pk) + "  deleted")
                order_number.delete()
                return HttpResponseRedirect(reverse(return_clients))

        except:
            return HttpResponseRedirect(reverse(return_clients))
        return render_to_response('delete_order.html', {'order':order, 'title':title, 'count':count, 'order_no':order_no }, context_instance = RequestContext(request))

Answer 1

delete() 对模型实例执行的操作之一是将其 pk 设置为 None，这样，如果您尝试保存它，它将创建一个新实例，而不是而不是尝试更新旧的（不再存在的）。

所以，简单的解决方案：在删除之前获取 PK。事实上，您可以删除对 delete 的第一次调用，因为您在创建消息后再次调用它。

顺便说一句，创建消息的更好方法是使用字符串格式：

message = "Previous order %s deleted" % order_number.pk

Answer 2

非常粗心的错误。为什么我的 order_number.delete() 写了两次？

if request.POST.get('delete'):
    order_number.delete() # Why was this there? of course, if I have this it will delete till it gets to the next part where it informs the user which order number was deleted! 
    request.user.message_set.create(message = "Previous order " + str(order_number.pk) + "  deleted")
    order_number.delete()

固定的