gistfile1.rb

class PluginHandler
  def initialize
    @plugins = Array.new
  end 

  def add(plugin)
    @plugins << plugin.send(:new)
  end 

  def delegate_method_to_plugins(method, *args)
    @plugins.each do |plugin|
      plugin.send(method, args) if plugin.respond_to? method
    end 
  end 

  def method_missing(method, *args)
    if method.to_s.match(/^on_/)
      delegate_method_to_plugins(method, *args)
    else
      super
    end 
  end 
end

class APlugin
  def on_connect(text)
    puts "APlugin#on_connect(#{text})"
  end 
end

ph = PluginHandler.new
ph.add(APlugin)
ph.on_nick
ph.on_connect("Hello world")