Bind your textarea

$(function(){
    data = ['tom','john'];
    $('textarea').atwho({at:"@", 'data':data});
});

that's it, check it out! more details in At.js Home Page

Issue command line bellow:
rails generate atwho:install
then It will show in public/[javascript|stylesheets]/ directory.

Add this gem in Gemfile like this:

gem 'jquery-atwho-rails'

add in app/assets/javascripts/application.js:

//= require jquery
//= require jquery.atwho

and in app/assets/stylesheets/applications.css:

//=require jquery.atwho

All in At.js project.

Just issue
bundle then appraisal rails30 rspec