Simple DSL pattern for configuration

config.rb

require 'singleton'

Config = Struct.new(:a, :b)

class Config
  include Singleton

  def self.[](arg)
    instance.public_send(arg.to_sym)
  end

  def self.config
    yield instance
  end
end

Config.config do |c|
  c.a = "something"
  c.b = "else"
end

puts Config[:a]
puts Config["b"]