parent controller_name (nested)

Hi people,
i have this route in rails

http://localhost:3002/gdm/9/cd/posts/10/comments

we can see we have a namespace with prefix in gdm/9/cd/

also we have two controllers

i will create a helper, and need get ther controllers name with commands

i know i can get “comments” with <%=controller_name%>

But how can i get “posts”

Sorry for my bad english =/

Thx