# this is in notifier.rb
module Notifier
  def print_done(msg);  puts "[+] #{msg}"; end
  def print_note(msg);  puts "[!] #{msg}"; end
  def print_error(msg); puts "[-] #{msg}"; end
end

# this is in where_i_wanna_use_this_notifier.rb
require 'notifier'
class WhereIWannaUseThisNotifier
  include Notifier

  def some_method
    if do_the_thing
      print_done "This thing was completed now."
    else
      print_error "ZOMG! It returned false!"
    end
  end
end