This gem provides a generator to download and install ace (Ajax.org Cloud9 Editor) into your Rails 3 project. It also provides some view helper to setup an editor.
Add the gem to your Gemfile and run bundle.
gem 'ace-rails'
Run the generator to download and install the current version of ace into public/javascripts/ace
rails g ace:install
Use the helper function to create an editor within your view
<%= ace_editor :mode => :css, :content => "body {\n\tfont-size: 12px;\n}" %>
the :mode option could be one of
[:c_cpp, :coffee, :css, :html, :java, :javascript, :php, :python, :ruby, :xml]
you can also specify a :theme option to change the look and feel of the ace editor. By default ace loads the textmate theme. Currentyl available themes are:
[:clouds, :clouds_midnight, :cobalt, :dawn, :eclipse, :idle_fingers, :kr_theme, :mongo_industrial, :monokai, :pastel_on_dark, :twilight]