allora ho il seguente codice ruby che sfrutta per la gui Gtk+ 2
codice:
if __FILE__ == $0
  # TODO Generated stub
  require "gtk2"
  $box
  
  def delete_event(widget , event)
      Gtk.main_quit
      return false
  end
  def create_label(widget)
    l = Gtk::Label.new("label")
    $box.pack_start(l,true,true,0)
    l.show
    
  end
  Gtk.init

  window = Gtk::Window.new(Gtk::Window::TOPLEVEL)
  window.set_title("ciao")
  window.signal_connect('delete_event') {|w,e| delete_event(w,e)}
  window.border_width = (100)
  button = Gtk::Button.new("Add")
  button.signal_connect('clicked') {|w| create_label(w)}
  $box = Gtk::HBox.new(false,0)

  window.add($box)
  $box.pack_start(button,true,true,0)
  button.show
  $box.show
  window.show

  Gtk.main
  
end
ma se lo avvio da eclipse mi da errore sul require "gtk2"
invece da terminale(sto su ubuntu) mi parte
perché?