gistfile1.rb

class AppServer
  attr_accessor :admin_password, :port
end

class Configuration
  attr_accessor :tail_logs, :max_connections, :admin_password

  def app_server
    @app_server ||= AppServer.new
    yield @app_server if block_given?
    @app_server
  end

end

def configure(&block)
  config = Configuration.new
  yield config if block_given?
  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.admin_password # => 'secret'  
p configuration.app_server.admin_password # => 'secret'