Django ORM验证数据库中的一行

Question

在我的网站上，买家搜索产品，找到产品后，他可以通过按联系按钮与卖家联系。如果两者之间存在关于该产品的对话，他应该被重定向到现有的对话，否则，我们创建一个新的对话。因此，对话由两个用户和一个列表定义。当我尝试实现逻辑时，我无法验证对话存在的两个条件，如果列表存在或用户存在 Django returns 则对话存在。这是我的代码：

def create_conversation(request, user_pk1, user_pk2, results_pk):
    user1 = get_object_or_404(get_user_model(), pk=user_pk1)
    user2 = get_object_or_404(get_user_model(), pk=user_pk2)
    results= get_object_or_404(Listing, pk=results_pk)
    existing_conversation = Conversation.objects.filter(users__in=[user1, user2]).filter(listing=results).values_list('id', flat=True)


    if existing_conversation.exists():

        return HttpResponseRedirect(reverse('conversation:conversation_update', kwargs={'pk':existing_conversation[0]}))
    else:
        conv=Conversation()
        conv.save()
        conv.listing = results
        conv.save()
        conv.users.add(*[user1,user2])
        return HttpResponseRedirect(reverse('conversation:conversation_update', kwargs={'pk': conv.pk}))

这是对话的模型：

class Conversation(models.Model):
    """
    Model to contain different messages between one or more users.

    :users: Users participating in this conversation.
    :archived_by: List of participants, who archived this conversation.
    :notified: List of participants, who have received an email notification.
    :unread_by: List of participants, who haven't read this conversation.]\['
    listing: the listing the conversation is about.
    read_by_all: Date all participants have marked this conversation as read.

    """
    users = models.ManyToManyField(
        settings.AUTH_USER_MODEL,
        verbose_name=_('Users'),
        related_name='conversations',
    )
# review the listing before going online, because it is necessary to have a conversation listing
    listing = models.ForeignKey (
        Listing,
        verbose_name=_('Listing'),
        related_name='listing',
        default= 1,
    )

及刊登型号：

class 列表(models.Model):

seller = models.ForeignKey(Profile, related_name='seller_listing', verbose_name='sellr', limit_choices_to={'is_seller': True})
    location_Country = models.CharField(max_length=45, verbose_name=_('from_Country'))
    location_State = models.CharField(max_length=45, verbose_name=_('from_State'), null=True, blank=True)
    location_City = models.CharField(max_length=45, verbose_name=_('from_City'))

我还尝试了一种将其分为两个条件的方法：a = conversation.objects.filter(users) 和 b= conversation.objects.filter(listing)，然后使用 if a and b then the conversation exists but遇到了同样的问题。

and existing_conversation = Conversation.objects.filter(Q(users__in=[user1, user2]) & Q(listing=results)).values_list('id', flat=True) 但遇到了同样的问题。预先感谢您的帮助。

Answer 1

您可以使用 django 的 intersection() 方法，自 Django 1.11 以来添加的运算符 return 两个或多个 QuerySet 的共享元素或按位操作 AND 与符号 `& 一起使用以获得相同的行为。

所以在你的情况下，检查两个用户之间是否有 & 或 intersection()

的交集

existing_conversation = (<b>user1.conversations.all() & user2.conversations.all()</b>).filter(listing=results)

# or with django intersection

existing_conversation = (user1.conversations.all()<b>.intersection</b>(user2.conversations.all())).filter(listing=results)

if existing_conversation.exists():
    return HttpResponseRedirect(reverse('conversation:conversation_update', 
       kwargs={'pk':<b>existing_conversation.first().pk</b>}))

 else:
    # rest of the code

BONUS, I see a typo in your code, you didn't send the pk as argument:

kwargs={'pk':<s>existing_conversation[0]</s>}

获取第一个实例 first() 并获取 pk

kwargs={'pk':<b>existing_conversation.first().pk</b>}

或

kwargs={'pk':<b>existing_conversation[0].pk</b>}

Django ORM验证数据库中的一行

Django ORM verification of a row in the database

django

python-3.x

django-models

django-orm