Easily setup class-level configurations with accessors and defaults

rails_class_configuration.rb

module ClassConfiguration
  extend ActiveSupport::Concern

  module ClassMethods
    def class_configuration(key, default = nil)
      class_attribute :"_#{key}"

      define_singleton_method(key) do |*args|
        if args.empty?
          return self.send(:"_#{key}") || default
        end

        self.send(:"_#{key}=", args.first)
      end

      define_method(key) do
        self.send(:"_#{key}") || default
      end
    end
  end

end