gistfile1.rb

class Configuration
  class AppServer
    attr_accessor :port, :admin_password
  end
  
  def initialize
    @app_server = AppServer.new
  end
  
  attr_accessor :tail_logs, :max_connections, :admin_password, :app_server

  def app_server
    block_given? ? yield(@app_server) : @app_server
  end
end

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

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