Django 休息 update_or_create

Question

背景:

我正在尝试创建一个系统，允许用户对其他用户撰写的评论进行投票(类似于 Reddit)。用户可以选择三个投票值:-1、0 或 1。我创建了一个 POST API(使用 django Rest-framework)，它将存储用户对特定评论的投票。如果用户已经对给定的评论进行了投票，那么它将把现有用户的投票值更新为新的投票值。

我从这篇文章中汲取了灵感:Django RF update_or_create

问题:

一旦评论让一个用户对其进行投票，每当另一个用户对同一评论进行投票时，Django 都会创建一个具有相同 ID/主键的重复评论对象。我截取了我的管理页面的屏幕截图，其中显示我有 3 个对象可供选择，但只有一条评论。为什么会这样做以及如何防止它？

Screenshot of my comment admin page

我是 Django 新手。我怀疑当我在序列化器中定义自己的“创建”方法时，我可能做错了什么。我将不胜感激任何帮助。谢谢!

models.py:

评论模型:

class Comment(models.Model):
    location_property_category = models.ForeignKey('locations.LocationPropertyCategory',on_delete=models.CASCADE,related_name='comments',null=True)
    author = models.ForeignKey('auth.User',on_delete=models.PROTECT,related_name='comments')
    location = models.ForeignKey('locations.Location',on_delete=models.CASCADE,related_name='comments')
    text = models.TextField()
    create_date = models.DateTimeField(default=timezone.now())
    published_date = models.DateTimeField(blank=True,null=True)
    approved_comment = models.BooleanField(default=False)

    objects = CommentManager()

    def approve(self):
        self.approved_comment = True
        self.save()

    def __str__(self):
        return self.text

    def save(self, *args, **kwargs):
        if self.approved_comment is True:
            self.published_date = timezone.now()
        super(Comment, self).save(*args, **kwargs)

    def sum_vote(self):
        return self.upvotedownvotes.aggregate(Sum('vote')).get('vote__sum') or 0

投票模型:

class UpVoteDownVote(models.Model):
    UPVOTE = 1
    NEUTRALVOTE = 0
    DOWNVOTE = -1

    VOTES = (
        (UPVOTE, 'Upvote'),
        (NEUTRALVOTE, 'Neutralvote'),
        (DOWNVOTE, 'Downvote')
    )

    vote = models.SmallIntegerField(choices=VOTES)
    user = models.ForeignKey('auth.User', related_name='upvotedownvotes', on_delete=models.CASCADE)
    comment = models.ForeignKey(Comment, related_name='upvotedownvotes', on_delete=models.CASCADE)
    date_voted = models.DateTimeField(default=timezone.now())

    class Meta:
        unique_together     = (('user','comment'),)

评论管理器模型:

class CommentManager(models.Manager):
    def get_queryset(self):
    return super(CommentManager, self).get_queryset().order_by('-upvotedownvotes__vote')

序列化器.py投票序列化器:

class UpVoteDownVoteSerializer(serializers.ModelSerializer):
    class Meta:
        model = UpVoteDownVote
        fields = ('vote','comment')

    def get_fields(self):
        fields = super(UpVoteDownVoteSerializer, self).get_fields()
        fields['comment'].queryset = Comment.objects.filter(approved_comment=True)
        return fields

    def create(self, validated_data):

        votedata, created = UpVoteDownVote.objects.update_or_create(
        user=validated_data.get('user', None),
        comment=validated_data.get('comment', None),
        defaults={'vote': validated_data.get('vote', None),
        })
        return votedata

views.py

class UpVoteDownVoteCreateApiView(generics.CreateAPIView):
    serializer_class = UpVoteDownVoteSerializer
    permission_classes = [IsAuthenticated]



    def perform_create(self,serializer):
        serializer.save(user=self.request.user)

评论应用admin.py

class CommentAdmin(admin.ModelAdmin):
    readonly_fields = ('id',)

admin.site.register(Comment,CommentAdmin)

Answer 1

欢迎来到 StackOverflow!

您的问题在 CommentManager 中:

queryset.order_by('-upvotedownvotes__vote')

此查询基本上创建LEFT_OUTER_JOIN。所以你的结果看起来像:

comment#1 upvote#1
comment#1 upvote#2
comment#1 upvote#3

这就是您看到评论#1 3 次的原因。

我相信你想使用这样的东西:https://docs.djangoproject.com/en/2.1/topics/db/aggregation/#order-by