DSL_metaprogrammed.rb

class ConfigurationClass
  def self.config_object(name, accessor, *methods)
    class_eval <<-EOS
      class #{name}
        attr_accessor *#{methods.inspect}
      end

      def #{accessor}
        @#{accessor} ||= #{name}.new
        yield @#{accessor} if block_given?
        @#{accessor}
      end
    EOS
  end
end

#class AppServer
#  attr_accessor :port, :admin_password
#end

class Configuration < ConfigurationClass
  attr_accessor :tail_logs, :max_connections, :admin_password
  config_object(:AppServer, :app_server, :port, :admin_password)
  config_object(:NameServer, :name_server, :port, :admin_password)
end


def configure(&block)
  config = Configuration.new
  block.call(config)
  config
end


### Just runs the 'tests' and prints results

configuration = configure do |config|  
  config.tail_logs = true  
  config.max_connections = 55  
  config.admin_password = 'secret'  
  config.app_server do |app_server_config|  
    app_server_config.port = 8808  
    app_server_config.admin_password = config.admin_password  
  end  
end  


puts configuration.class #=> Configuration  
puts configuration.tail_logs #=> true  
puts configuration.app_server.admin_password #=> 'secret'  

pass = true
pass &&= configuration.class == Configuration
pass &&= configuration.tail_logs == true
pass &&= configuration.app_server.admin_password == 'secret'

puts "\nResult: #{pass ? '\o/' : ':('}"

My god that's ugly :-)