The Dynamic Languages Toolkit (DLTK) plugin is a popular method to work with Ruby in Eclipse. Aptana has a Ruby/Rails plugin, but most programmers seem to recommend the DLTK plugin over it.
To install the DLTK Ruby plugin:
Install Eclipse, if you do not already have it. I like to start off with a minimal Eclipse installation.
Go to Help -> Install New Software. From the dropdown choose All Available Sites. After the list below fills up, choose Programming Languages -> Dynamic Languages Toolkit - Ruby Development Tools. Install it and restart Eclipse.
Configure the Ruby or JRuby interpreter you want to use in Window -> Preferences -> Ruby -> Interpreters.
You can create Ruby projects and edit, run and debug
.rb files now in Eclipse! 😊
Tried with: DLTK Ruby 5.0.0, Eclipse 4.4.1 and Ubuntu 14.04