Programming Ruby 3.3

Official Ruby Typing with RBS

The official Ruby typing system is called RBS (short for Ruby Signature). With RBS, you create a separate file that contains type signature information for all or part of your code.

Writing RBS

To take a look at how RBS works, we’ll use the gem we created in ​Writing and Packaging Your Own Code into Gems​, and augment it with RBS typing. If you look at the Aaagmnr gem code, you’ll see that it contains a directory named sig that we didn’t talk much about. That directory is where you’re supposed to put the type information, and right now it contains one file:

gems/aaagmnr/sig/aaagmnr.rbs

module Aaagmnr
  VERSION: String
  # See the writing guide of rbs: https://github.com/ruby/rbs#guides
end

The only thing this file ...