(django)如何获取有效形式的对象id?

我正试图用django在一个发布应用上做一个评论表单,问题是我似乎无法获得它自己对象的id,知道吗?

#views.py
class MyFormView(FormView):
    form_class = CommentForm
    success_url = "/"

    def form_valid(self,form,*args,**kwargs):
        comment = form.save(commit=False)
        comment.message=Message.objects.get(id=???)
        comment.save()
        return super(MyFormView, self).form_valid(form)

#urls.py
urlpatterns = [
    path('', MessageListView.as_view(),name="messaging-main"),
    path('new', MessageCreateView.as_view(),name="messaging-new"),
    path('post/<int:pk>', MessageDetailView.as_view(),name="messaging-detail"),
    path('my_form',MyFormView.as_view(),name="form-view")
]

#forms.py
class CommentForm(forms.ModelForm):
    class Meta:
        model = Comment
        fields = ['comment']

#models.py
class Message(models.Model):
    date_posted = models.DateTimeField(default=timezone.now)
    message = models.TextField()
    image = models.ImageField(default="")


    def __str__(self):
        return self.message

class Comment(models.Model):
    message = models.ForeignKey(Message,on_delete=models.CASCADE)
    comment = models.TextField(max_length=50)
    date_posted = models.DateTimeField(default=timezone.now)

    def __str__(self):
        return "Comment on {}".format(str(self.date_posted))

    def get_absolute_url(self):
        return reverse("messaging-detail",kwargs={"id":self.id})

如果我要替换???对于示例7,它将在id为7的消息(或post)上发布每个评论,但我希望将评论发布到我看到的消息上感谢任何帮助