```ruby
class ForumTopic < ActiveRecord::Base
  has_many :posts, class_name: 'ForumPost', foreign_key: :topic_id
end
```

Make forum topics sluggable too.
user
```ruby
class ForumTopic < ActiveRecord::Base
  has_many :posts, class_name: 'ForumPost', foreign_key: :topic_id

  is_sluggable :title, history: false

end
```
assistant