Use specific version of gem "jquery-rails", "~> 2.3.0" as later version of gem has deleted the ui part.
or
you can use gem "jquery-ui-rails" for jquery-ui . For more information please visit the git repository
To require all jQuery UI modules, add the following to your application.js:
for version 5.0 and more it has been changed. Please follow the link
application.js:
//= require jquery-ui
application.css:
/*
*= require jquery-ui
*/
For lesser version than 5.0 we need to write below format
application.js:
//= require jquery.ui.all
Also add the jQuery UI CSS to your application.css:
application.css:
/*
*= require jquery.ui.all
*/
Hope this could help you