observer.rb

require "observer"
require "dxruby"

class Observer
  include Observable
end

class O
   attr_accessor :x , :y , :d , :func
   def initialize  x , y , d , func
     @x = x
     @y = y
     @d = d
     @func  = func
   end
   def update *h
     @func.call self
   end
end
task    = Observer.new
us_task = Observer.new 
task.add_observer O.new  200 , 300 , Image.new(50,50,[200,220,170]) , ->o do
  o.x += Input.x * 4
  o.y += Input.y * 4
  Window.draw o.x , o.y , o.d
  if Input.keyPush? K_Z
    us_task.add_observer O.new o.x , o.y , Image.new(10,5,[200,220,170]) , ->o do
      o.y -= 3
      if o.y < 0
        us_task.delete_observer o
      end
      Window.draw o.x , o.y , o.d
    end
  end
end
  
font  = Font.new 20
Window.loop do
  exit if Input.keyPush? K_F9
  task.changed
  task.notify_observers
  us_task.changed
  us_task.notify_observers

  Window.drawFont 50 , 50 ,    task.count_observers.to_s , font 
  Window.drawFont 50 , 80 , us_task.count_observers.to_s , font 

end