ios - NSTimer ミリ秒のカウントダウン

Question

秒とミリ秒の単純なカウントダウンを作成したいと思います: SS:MM. しかし、タイマーを止めるか、タイマーが0:00になったら何かをしたいです。現在、タイマーは動作していますが、0:00 で止まりません。秒を止めることはできますが、ミリ秒を止めることはできません。なにが問題ですか？

-(void) setTimer {
    MySingletonCenter *tmp = [MySingletonCenter sharedSingleton];
    tmp.milisecondsCount = 99;
    tmp.secondsCount = 2;



    tmp.countdownTimerGame = [NSTimer scheduledTimerWithTimeInterval:.01 target:self selector:@selector(timerRun) userInfo:nil repeats:YES];


}

-(void) timerRun {
    MySingletonCenter *tmp = [MySingletonCenter sharedSingleton];
    tmp.milisecondsCount = tmp.milisecondsCount - 1;



    if(tmp.milisecondsCount == 0){
        tmp.secondsCount -= 1;

        if (tmp.secondsCount == 0){

            //Stuff for when the timer reaches 0
            //Also, are you sure you want to do [self setTimer] again
            //before checking if there are any lives left?

            [tmp.countdownTimerGame invalidate];
            tmp.countdownTimerGame = nil;
            tmp.lives = tmp.lives - 1;
            NSString *newLivesOutput = [NSString stringWithFormat:@"%d", tmp.lives];
            livesLabel.text = newLivesOutput;
            if (tmp.lives == 0) {
                [self performSelector:@selector(stopped) withObject:nil];

            }
            else {[self setTimer]; }
        }
        else

            tmp.milisecondsCount = 99;
    }


    NSString *timerOutput = [NSString stringWithFormat:@"%2d:%2d", tmp.secondsCount, tmp.milisecondsCount];

    timeLabel.text = timerOutput;






}



-(void) stopped {
    NSLog(@"Stopped game");
    timeLabel.text = @"0:00";

}