If I have previously used a method that is not yet defined, I can def + tab to create a new method and “create_method” will automatically be highlighted.

But it does not provide completion options as I type. For example, in the attached image, bubbles has already been used and should thus be an option when I type ‘b’ as the first letter of the method name.

Screen Shot 2013-03-09 at 2.34.08 PM.png654×624 24.4 KB

The list does not pop up automatically, but you can make it appear with ctrl+space. If you want it to pop up automatically, I guess you have to play with the .tmPreferences files of the Ruby package (but I did not manage to get it this way).
Hope this helps.
– Thierry