python - 如何修复 Django 中的 'The QuerySet value for an exact lookup must be limited to one result using slicing.' 错误

Question

我正在尝试返回 Django View 中过滤后的 qweryset 的计数。如何实现这一目标，同时避免“精确查找的 QuerySet 值必须限制为使用切片的一个结果”。错误？

我尝试使用 len() 但仍然遇到相同的错误。

这是我的代码:

型号

class Post(models.Model):
    STATUS_CHOICES = (
        ('draft', 'Draft'),
        ('published', 'Published'),
    )

    title = models.CharField(max_length=200)
    slug = models.SlugField(max_length=200)
    author = models.ForeignKey(settings.AUTH_USER_MODEL, 
                              on_delete=models.CASCADE)
    body = models.TextField()
    category = models.ForeignKey(Category, on_delete=models.CASCADE, 
                                  blank=True, null=True)
    read_time = models.CharField(max_length=256, null=True, blank=True)
    count_visits = models.IntegerField(default=0)
    publish = models.DateTimeField(default=timezone.now)
    created = models.DateTimeField(auto_now_add=True)
    updated = models.DateTimeField(auto_now=True)
    status = models.CharField(max_length=10, choices=STATUS_CHOICES, 
                              default='published')

    class Meta:
        ordering = ('-publish',)

    def __str__(self):
        return self.title

    def get_absolute_url(self):
        return reverse('blog:blog_post', args=[self.slug])

    def get_body_as_markdown(self):
        return mark_safe(markdown(self.body, safe_mode='escape'))

class PostView(models.Model):
    post = models.ForeignKey(Post, on_delete=models.SET_NULL, null=True,
                             related_name='postviews')
    ip = models.CharField(max_length=50)
    http_host = models.CharField(max_length=256, null=True, blank=True)
    http_referrer = models.CharField(max_length=256, null=True, blank=True)
    http_user_agent = models.CharField(max_length=256, null=True, blank=True)
    remote_host = models.CharField(max_length=256, null=True, blank=True)

    created = models.DateTimeField(auto_now_add=True)
    updated = models.DateTimeField(auto_now_add=True)

    def __str__(self):
        return self.ip

浏览次数:

class PostDetailView(DetailView):
    model = Post
    template_name = 'blog/post.html'
    context_object_name = 'post'

    def get(self, request, *args, **kwargs):
        self.slug = get_object_or_404(Post, slug=self.kwargs['slug'])
        p = Post.objects.filter(slug=self.slug)
        count_visits = None
        unique_views = set()

        if self.request.user.is_authenticated:
            post_views = PostView.objects.filter(post=p)
            count_visits = post_views.count()
            for post_view in post_views:
                unique_views.add(post_view.ip)

        else:
            post_view = PostView(ip=request.META.get('REMOTE_ADDR', ''),
                      http_host=request.META.get('HTTP_HOST', ''),                             
                      http_referrer=request.META.get('HTTP_REFERER',''),                               
                      http_user_agent=request.META.get('HTTP_USER_AGENT',''),
                      remote_host=request.META.get('REMOTE_HOST', ''))

            post_view.save()

        c = {
            'count_visits': count_visits,
            'unique_views': unique_views,
        }
        return render(request, self.template_name, c)

模板:

<span>
    {% if user.is_authenticated %}
      <br>
      {{ count_visits }} views, {{ unique_views|length }} unique views.
    {% endif %}
</span>

我希望输出显示模板中的 View 数量，但我收到“精确查找的 QuerySet 值必须限制为使用切片的一个结果”。错误。

非常感谢!

Answer 1

改变这个

p = Post.objects.filter(slug=self.slug)

至此

p = Post.objects.filter(slug=self.slug)[0]

错误:

filter 返回一个查询集，即使只有一个元素匹配。

PostView.objects.filter(post=p) 失败，因为它期望 post 是一个对象而不是查询集。

更新:

self.slug不会被初始化，因为实例变量只能在__init__内部声明。

您只需删除 self 部分即可将slug 标记为局部变量

slug = get_object_or_404(Post, slug=self.kwargs['slug'])
p = Post.objects.filter(slug=slug)