mb_progress_hud.rb

class MBProgressHUD
  def rac_command=(command)
    self.rac_liftSelector "hud_visible=:", withObjects: rac(command).executing.startWith(command.isExecuting).boolean
  end

  def hud_visible=(visible)
    if visible
      self.show true
    else
      self.hide true
    end
  end
end