view

class PostDetailView(FormMixin,DetailView):
    model = Post
    template_name = 'post/post_detail.html'
    form_class = CommentForm

    def get_success_url(self):
        return reverse('post-detail', kwargs={'pk': self.object.id})

    def get_context_data(self, **kwargs):

        context = super(PostDetailView, self).get_context_data(**kwargs)
        context['comments'] = Comment.objects.filter(post=self.object)
        context['form_comment'] = CommentForm(initial={'post': self.object})
        return context

    def post(self, request, *args, **kwargs):
        self.object = self.get_object()
        form = self.get_form()
        if form.is_valid():
            return self.form_valid(form)
        else:
            return self.form_invalid(form)

    def form_valid(self, form):
        form.instance.user = self.request.user
        form.instance.post = self.object
        form.save()
        return super(PostDetailView, self).form_valid(form)



models
class Post(models.Model):
    title = models.CharField(max_length=100, verbose_name='Заголовок')
    content = models.TextField(verbose_name='Содержание')
    date_posted = models.DateTimeField(default=timezone.now,
                                       verbose_name='Время', null=True, blank=True)
    author = models.ForeignKey(User, on_delete=models.CASCADE,
                               verbose_name='Автор', blank=True)


    def __str__(self):
        return self.title

    def get_absolute_url(self): #дает возможность сылаться на пост для детаил вью
        return reverse('post-detail', kwargs={'id': self.id})

class Comment(models.Model):

    user = models.ForeignKey(User, on_delete=models.CASCADE)
    post = models.ForeignKey(Post, on_delete=models.CASCADE)
    content = models.TextField(max_length=500, verbose_name='')
    timestamp = models.DateTimeField(auto_now_add=True,
                                       verbose_name='Время', null=True, blank=True)
    reply = models.ForeignKey('Comment', on_delete=models.CASCADE, null=True, blank=True, related_name='replies')

    class Meta:
        ordering = ['-timestamp']

    def __str__(self):
        return '{}'.format(self.content)