Write the code for iframe and in the src option give the path that defined in routes. It will render the file which corresponding action of the controller renders.
An Haml example is given below:
%iframe{:align => "center", :name => "window", :src => "#{list_make_shipments_path(:ids => "#{@shipment_success_responses.collect(&:id).join(",")}")}", :height => "1000px;", :width => "1100px;", :style => "float:left;margin-top:30px;"}
The Rails Drop 