在views/cpanel/node视图和model/node.rb模型中分别添加f.slug和field :slug后，再在 topic.rb 模型中 cache node_slug，就可以通过修改 routes 来 cheat 了：

{"movies" => 1, "books" => 2, "music" => 3}.each do |slug, id|
  match "#{slug}" => "topics#node", :as => "#{slug}".to_sym, :id => id
  match "#{slug}/new" => "topics#new", :as => "new_#{slug}".to_sym, :node_id => id
end

以及 feed 的 routs:

{"movies" => 1, "books" => 2, "music" => 3}.each do |slug, id|
  match "#{slug}/feed" => "topics#node_feed", :as => "feed_#{slug}".to_sym, :id => id
end

然后，修改一下render_node_name方法

def render_node_name(name, slug)
  link_to(name, "/#{slug}" )
end

在views/topics/_topic.html.erb以及views/topics/_topic_info.html.erb中调用render_node_name的参数 node_id 改为 node_slug

最后，再修改一下render_topic_node_select_tag方法：

  def render_topic_node_select_tag(topic, node_id)
    return if topic.blank?
# 我喜欢扁平式的node结构，所以取消了group_collection_select，而使用了collection_select
#    grouped_collection_select :topic, :node_id, Section.all, 
#                    :sorted_nodes, :name, :id, :name, :value => topic.node_id,
#                    :include_blank => true, :prompt => "选择节点"
     collection_select :topic, :node_id, Node.all,
                     :id, :name, :value => topic.node_id,
                     :include_blank => true, :prompt => "选择主题类型",
                     :selected => node_id 
  end

这样，就支持类似

ruby-china.org/slug

ruby-china.org/slug/new

这样的访问方式啦。