Please try this really cool extension for Spotlight on Mac:
As you see you can now use RB Class in the search criteria popup and look explicit for projects using a given class name:
On Oct 30, 2015, Thomas Tempelmann has released a new version of the Spotlight importer for Xojo.
It allows Spotlight to search projects saved by the Xojo (and Real Studio) IDE.
The importer used to be included in Real Studio and early Xojo IDEs until about 2 years ago. This version by Thomas Tempelmann is functionally the same, as a standalone plugin, and updated to support the latest Xojo project formats.
More information and download here: tempel.org/RB/SpotlightImporter
And of course you have full text search in your Xojo and Real Studio projects.