In Aptana(or Eclipse) with RadRails, if you use the Emacs keybinding Scheme, you would find that the Content Assist shortcut Alt+/ doesn’t work (as the Ctrl + Space under Default Scheme). Apparently this shortcut was left out by the RDT. So here’s the way to add it manually:

• Go to Window > Preferences > General > Keys
• Make sure the Emacs Scheme is selected under Modify tab
• Under Command, select Edit in the Category list and select Ruby Content Assist in the Name list
• Under Key Sequence, focus on the Name field, press “Alt + /”, then select Ruby Editor in the When list
• Click Add, then click OK to close the Preferences dialog
• Open a ruby source file to confirm that the Alt + / works