#ruby-202001101116.rb

# https://ruby-doc.org/stdlib-2.7.0/libdoc/ostruct/rdoc/OpenStruct.html
require 'ostruct'

module Configurable
  def config(&block)
    @config ||= OpenStruct.new
    return @config unless block_given?
    @config.tap(&block)
  end
end

module Foo
  extend Configurable
  
  # setting defaults
  config.some_value = 'default value'
  config.another = 'default value'
  
  class << self
    def some_method
      puts "do something with #{config.some_value}"
    end
  end
end

Foo.some_method
# prints: do something with default value

# in some initializer
Foo.config do |config|
  config.some_value = 'configured value'
end

Foo.some_method
# prints: do something with configured value