Django删除评论后重定向文章详情页报错：function object has no attribute 'format'

我想要实现删除指定pk的评论后自动重定向到对应文章的详情页，但点击评论删除按钮时总会触发AttributeError，错误提示为function object has no attribute 'format'。如果把评论删除视图的success_url改成无参数的列表页重定向就能正常运行，但这不是我想要的效果。

相关代码 #

Post模型

class Post(models.Model):
    STATUS_CHOICES = (
        ('draft', 'Draft'),
        ('published', 'Published'),
    )
    title = models.CharField(max_length=250)
    slug = models.SlugField(max_length=250, unique_for_date='publish')
    author = models.ForeignKey(get_user_model(), on_delete=models.CASCADE, related_name='blog_posts')
    body = models.TextField()
    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')
    objects = models.Manager()
    published = PublishedManager()
    tags = TaggableManager()

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

    def __str__(self):
        return self.title

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

    def save(self, *args, **kwargs):
        self.slug = slugify(self.title)
        super().save(*args, **kwargs)

Comment模型

class Comment(models.Model):
    post = models.ForeignKey(Post, on_delete=models.CASCADE, related_name='comments')
    author = models.ForeignKey(get_user_model(), on_delete=models.CASCADE,)
    comment = models.TextField()
    created = models.DateTimeField(auto_now_add=True)
    updated = models.DateTimeField(auto_now=True)
    active = models.BooleanField(default=True)

    class Meta:
        ordering = ('created',)

    def __str__(self):
        return f'Comment by {self.author} on {self.post}'

    def get_absolute_url(self):
        return self.post.get_absolute_url() + f'#comment-{self.pk}'

CommentDeleteView视图

class CommentDeleteView(DeleteView):
    model = Comment
    template_name = 'comment_delete.html'
    def success_url(self):
        post = Post.objects.get(pk=self.object.post.pk)
        return post.get_absolute_url()

完整报错信息 #

Internal Server Error: /blog/13/comment_delete/
Traceback (most recent call last):
  File "C:\Users\SUNNY\blog_folder\ven\lib\site-packages\django\core\handlers\exception.py", line 34, in inner
    response = get_response(request)
  File "C:\Users\SUNNY\blog_folder\ven\lib\site-packages\django\core\handlers\base.py", line 115, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "C:\Users\SUNNY\blog_folder\ven\lib\site-packages\django\core\handlers\base.py", line 113, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "C:\Users\SUNNY\blog_folder\ven\lib\site-packages\django\views\generic\base.py", line 71, in view
    return self.dispatch(request, *args, **kwargs)
  File "C:\Users\SUNNY\blog_folder\ven\lib\site-packages\django\views\generic\base.py", line 97, in dispatch
    return handler(request, *args, **kwargs)
  File "C:\Users\SUNNY\blog_folder\ven\lib\site-packages\django\views\generic\edit.py", line 218, in post
    return self.delete(request, *args, **kwargs)
  File "C:\Users\SUNNY\blog_folder\ven\lib\site-packages\django\views\generic\edit.py", line 212, in delete
    success_url = self.get_success_url()
  File "C:\Users\SUNNY\blog_folder\ven\lib\site-packages\django\views\generic\edit.py", line 222, in get_success_url
    return self.success_url.format(**self.object.__dict__)
AttributeError: 'function' object has no attribute 'format'
[19/Jun/2020 11:50:28] "POST /blog/13/comment_delete/ HTTP/1.1" 500 88418

问题原因与解决方案 #

核心原因 #

Django的DeleteView（以及其他通用编辑视图）中，success_url如果是类属性的话，框架会自动尝试用format方法把它和当前对象的属性进行格式化。但你在这里把success_url定义成了一个方法（函数），框架依然会把它当成字符串去调用format，自然就会抛出"函数对象没有format属性"的错误。

正确的做法是重写get_success_url()方法，而不是定义success_url函数。

修改后的代码 #

把你的CommentDeleteView修改成下面这样：

class CommentDeleteView(DeleteView):
    model = Comment
    template_name = 'comment_delete.html'
    
    def get_success_url(self):
        # 不需要重新查询Post，self.object就是当前要删除的Comment实例
        return self.object.post.get_absolute_url()

说明 #

• 重写get_success_url()方法是Django通用视图中自定义成功跳转地址的标准方式，框架会自动调用这个方法来获取跳转URL，而不是去尝试格式化success_url属性。
• 直接通过self.object.post就能拿到评论对应的文章对象，不需要再用Post.objects.get()去查询，既简洁又高效。

这样修改之后，删除评论就能正确重定向到对应文章的详情页了。

内容的提问来源于stack exchange，提问作者honesty20