gistfile1.txt

- (IBAction)buttonPressed:(id)sender {
  if (timer == nil) {
    seconds = 30;
    timer = [[NSTimer scheduledTimerWithTimeInterval:1.0
                                              target:self
                                            selector:@selector(updateCounter:)
                                            userInfo:nil
                                             repeats:YES] retain];
  }
}

- (void)updateCounter:(NSTimer *)theTimer {
  if (seconds > 0) {
    --seconds;
  } else {
    seconds = 30;
    [timer invalidate];
    [timer release];
    timer = nil;
  }
  self.myCounterLabel.text = [NSString stringWithFormat:@"%d", seconds];    
}