protected function can_post($course, $forum, $discussion, $post, $cm, $context) {
        if (!isset($this->canpostto[$discussion->id])) {
            $this->canpostto[$discussion->id] = forum_user_can_post($forum, $discussion, $this->recipient, $cm, $course, $context);
        }
        return $this->canpostto[$discussion->id];
    }