gistfile1.rb

class Controller
  attr_accessor :timer
  def startTimer(sender)
    @timer = Timer.new
    timerThread = NSThread.alloc.initWithTarget(@timer,
                                          selector:'startTimer:',
                                          object:'dummy_obj' )
    timerThread.start
  end
end

class Timer
  attr_accessor :input
  def startTimer(to_process)
    @startTime = Time.now
    interval = NSTimer.timerWithTimeInterval 0.1, 
                         target: self, 
                         selector: "update_timer:", 
                         userInfo: nil, 
                         repeats: true
    NSRunLoop.currentRunLoop.addTimer(interval, forMode: NSDefaultRunLoopMode)
    NSRunLoop.currentRunLoop.runUntilDate(NSDate.distantFuture)
  end
    
  def update_timer(timer)
    elapsed = Time.now - @startTime
    @input.setDateValue(NSDate.dateWithString(@elapsed.to_s))
  end  
end