callbacks.rb

module Callbacks
  
  def callbacks
    @_callbacks ||= {}
  end
  
  def bind(callback_name, &block)
    callbacks[callback_name] ||= []
    callbacks[callback_name] << block
  end
  
  def unbind(callback_name)
    callbacks.delete callback_name
  end
  
  def trigger(callback_name)
    return unless callbacks[callback_name]
    callbacks[callback_name].each do |block|
      block.call
    end
  end
end


# TEST ::::::::::::::::::::::

class Test
  include Callbacks
end

test = Test.new

test.bind :talk do
  puts 'Hello!'
end

test.bind :talk do
  puts 'I am talking!'
end

test.trigger :talk