public function saveAfter(Post $previous)
 {
     // If the previous post is another 'discussion locked' post, and it's
     // by the same user, then we can merge this post into it. If we find
     // that we've in fact reverted the locked status, delete it. Otherwise,
     // update its content.
     if ($previous instanceof static && $this->user_id === $previous->user_id) {
         if ($previous->content['locked'] != $this->content['locked']) {
             $previous->delete();
         } else {
             $previous->content = $this->content;
             $previous->save();
         }
         return $previous;
     }
     $this->save();
     return $this;
 }
 public function saveAfter(Post $previous)
 {
     // If the previous post is another 'discussion tagged' post, and it's
     // by the same user, then we can merge this post into it. If we find
     // that we've in fact reverted the tag changes, delete it. Otherwise,
     // update its content.
     if ($previous instanceof static && $this->user_id === $previous->user_id) {
         if ($previous->content[0] == $this->content[1]) {
             $previous->delete();
         } else {
             $previous->content = static::buildContent($previous->content[0], $this->content[1]);
             $previous->time = $this->time;
             $previous->save();
         }
         return $previous;
     }
     $this->save();
     return $this;
 }