exercise from Charity Tutorial at Scottish Ruby Conf: configuration DSL

configuration.rb

class AppServerConfiguration
  attr_accessor :port, :admin_password
end

class Configuration 
  
  attr_accessor :tail_logs, :max_connections, :admin_password
  
  def initialize(block)
    block.call(self)
  end
  
  def app_server
    if block_given?
      @app_server_config = AppServerConfiguration.new
      yield @app_server_config
    else
      @app_server_config
    end
  end
  
end

def configure(&b)
  Configuration.new(b)
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'