configuration.rb

require 'yaml'

class Configuration
  def self.load_yaml(file)
    new(YAML.load_file(file))
  end

  def initialize(config, schema=nil)
    config.each do |key, value|
      value = Configuration.new(value) if value.is_a?(Hash)
      instance_variable_set(:"@#{key}", value)
    end

    singleton_class.send :attr_reader, *config.keys
  end

  def [](name)
    ivar = :"@#{name}"
    raise KeyError, "key not found: #{name.inspect}" unless instance_variable_defined?(ivar)

    instance_variable_get(ivar)
  end
end