NSTimer jumping 2 seconds

Question

Please help,

I have a NSTimeInterval which I convert into a NSDateComponent and then assign each component (year, month, day, etc) to an appropriate label. After I do the conversion I start an NSTimer to begin a countdown. Here's the code I use:

- (void)configureView
{
    if (self.detailItem) {
        self.progressView.progress = 0.0;
        self.initialInterval = [[self.detailItem valueForKey:@"date"] timeIntervalSinceNow];
        self.timeElapsed = self.initialInterval;
        self.secondsLeft = [self resetLabel];
        NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:1
                                                          target:self
                                                        selector:@selector(timerFireMethod:)
                                                        userInfo:nil
                                                         repeats:YES];
    }
}

- (void)timerFireMethod:(NSTimer *)timer
{
    if (self.secondsLeft > 0) {
        self.secondsLeft--;
        self.timeElapsed--;
        [self updateSecondsWithNumber:self.secondsLeft];
        self.progressView.progress = 1 - (self.timeElapsed / self.initialInterval);
    } else {
        if (self.timeElapsed <= 0) { [timer invalidate]; return; }
        [self resetLabel];
        self.secondsLeft = 59;
    }
}

- (void)updateSecondsWithNumber:(int)number
{
    self.secondLabel.text = [NSString stringWithFormat:@"%ds", number];
}

- (NSTimeInterval)resetLabel
{
    NSDateComponents *convertedInfo = [ChronoModel dateComponentFromTimeInterval:self.timeElapsed];
    self.yearLabel.text = [NSString stringWithFormat:@"%ldy", (long)convertedInfo.year];
    self.monthLabel.text = [NSString stringWithFormat:@"%ldm", (long)convertedInfo.month];
    self.dayLabel.text = [NSString stringWithFormat:@"%ldd", (long)convertedInfo.day];
    self.hourLabel.text = [NSString stringWithFormat:@"%ldh", (long)convertedInfo.hour];
    self.minuteLabel.text = [NSString stringWithFormat:@"%ldm", (long)convertedInfo.minute];
    self.secondLabel.text = [NSString stringWithFormat:@"%lds", (long)convertedInfo.second];
    return convertedInfo.second;
}

timeElapsed, initialInterval and secondsLeft are all NSTimeIntervals.

For some reason the label jumps two seconds instead of just one. I have no idea why this is happening. Any ideas?

Thank you.

Answer 1

My best guess is that you have two instances of the timer running. Try putting an NSLog ahead of the [NSTimer scheduledTimerWithTimeInterval line.