plugin.rb

module PluginSugar
  def def_field(*names)
    class_eval do 
      names.each do |name|
        define_method(name) do |*args| 
          case args.size
          when 0: instance_variable_get("@#{name}")
          else    instance_variable_set("@#{name}", *args)
          end
        end
      end
    end
  end
end

class Plugin
  @registered_plugins = {}
  
  class << self
    attr_reader :registered_plugins
    private :new
  end

  def self.define(pattern, &block)
    p = new
    p.instance_eval(&block)
    Plugin.registered_plugins[pattern] = p
  end

  extend PluginSugar
  def_field :name, :details, :version, :usage
end