Finding layouts

I'm trying to find out whether a particular layout file exists at runtime. I need to potentially change the layout depending on which "site" a customer is visiting. I can do this by calling a method in the controller to determine the layout similar to:

   def customer_layout
     if @site_id.nil?
       return "customer_standard"
     else
       return "customer_site_" + @site_id.to_s
     end
   end

I need to determine if a particular site does indeed have a custom layout, if not then fall back to the standard one. So I need to see if "customer_site_123.rhtml" actually exists in the layout directory. The problem is I don't want to hard code absolute paths that are certain to change on deployment.

Is there a way to determine what the current layout directory is so I can use that to try and find the file?

Eventually this will apply to css and image folders so any pointer there will help too.

Thanks,
Gary.

RAILS_ROOT is the "top" of your application, so you can do a check like:

   File.exists?("#{RAILS_ROOT}/app/views/layouts/somefile.rhtml")