It shouldn't be this hard

include.rb

module Hi
  def self.included(base)
    base.class_eval do #Enumerable
      def hello
        puts "hello"
      end
    end
  end
end

module Enumerable
  include Hi
end

[].hello # "hello"

hi, quick random question. what does the def :hello accomplish when used this way inside a do-block code?

By using base.class_eval, the hello method is being defined in the context of the module or class that includes the Hi module. In this example, this means that the hello method is available on all instances of classes that include Enumerable – like Array, Hash, etc. This, in effect, is the same thing as adding the hello method definition directly to Enumerable.

thanks, got it.