Django - Catch argument in Class based FormView

On my page, i need to display the post detail and a comment form for viewer to post comment. I created 2 generic views: ``` # views.py class PostDetailView (DetailView): model = Post context_object_name = 'post' template_name = 'post.html' def get_context_data(self, **kwargs): context = super(PostDetailView, self).get_context_data(**kwargs) context['comment_form'] = CommentForm() return context class AddCommentView(FormView): template_name = 'post.html' form_class = CommentForm success_url = '/' def form_valid(self, form): form.save() return super(AddCommentView, self).form_valid(form) def form_invalid(self, form): return self.render_to_response(self.get_context_data(form=form)) detail = PostDetailView.as_view() add_comment = AddCommentView.as_view() # urls.py .... url(r'^(?P<pk>\d+)/$', view='detail'), url(r'^(?P<post_id>\d+)/add_comment/$', view='add_comment'), .... ``` Error would occur in the AddCommentView,since I haven't specified the post's id for the comment. How can I access the post_id in the AddCommentView?