倒计时功能

# pragma mark - 定时器
- (void) addCountDownTimer {
       if(self.timer != nil) {
       [self.timer invalidate];
       self.timer = nil;
        }
    self.timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(startCountDown) userInfo:nil repeats:YES];
    [[NSRunLoop currentRunLoop] addTimer:self.timer forMode:NSRunLoopCommonModes];
}

- (void) startCountDown {
    _allCount -= 1000;
    NSTimeInterval courrentAllCount = _allCount / 1000;
    NSDate *date = [NSDate dateWithTimeIntervalSince1970:courrentAllCount];
    // DateTools 第三方框架
    self.statusMsgLb.text = [NSString stringWithFormat:@"剩%@%@", [date formattedDateWithFormat:@"dd天HH时"],_countTitle];
     if (0 >= _allCount) {
        [self removeCountDownTimer];
    }
}

// 移除定时器
- (void) removeCountDownTimer {
    if(self.timer != nil) {
    [self.timer invalidate];
    self.timer = nil;
    }
}