Попробуйте это
<%= link_to_remote, 'Message', :url=>{:controller=>'controller_name', :action=>'method_name'}, :with=> "'msg='+msg" %>
controller_name.rb
def method_name
@message= params[:msg]
puts @message # >> should be print "Hello World"
end
отредактировано
<%= link_to_remote, 'Message', :url=>{:controller=>'controller_name', :action=>'method_name'}, :with=> "'msg='+msg" %>
<div id ='show_message'></div>
controller_name.rb
def method_name
@message= params[:msg]
render :update do|page|
page.replace_html 'show_message', @message
end
end