Render_to_string() in a controller that isn't default route?

Rails
1

Is it possible to call render_to_string() in a controller that is not
set as the default route?

The content controller is set in routes.rb: map.connect ‘’, :controller
=> “content”. The content controller is calling a template controller,
and I would like to be able to call render_to_string() within the
template controller, however I receive the error:

 undefined method `render_to_string' for TemplateController:Class

I’ve tried directly require()'ing the ActionController Base class file
which defines the render_to_string function (not a solution I would want
to use - that was more out of curiousity), and that didn’t work.

Thanks in advance.