unborn.rb

require 'observer'

class Iraci < Struct.new(:name, :birth_date)
  include Observable
  def birth!
    self[:birth_date] = Time.now.strftime('%d %B')
    changed
    notify_observers(name, birth_date)
  end
end

class Observer
  def initialize(observed)
    observed.add_observer(self)
  end

  def update(name, birth_date)
    puts "#{name} has been constructed on #{birth_date}"
  end
end

unborn = Iraci.new 
pallotron = Observer.new(unborn)

# Ivan, please set the name of the unborn when you 
# and your wife will decide; once delivered, just call 
# the birth! method on the unborn to notify the observer :)