ios 倒计时例子

//类变量 
int seconds;
NSTimer *timer;

//启动
-(void)startTimer
{
    seconds = 86400*2+3600+60+24; //2天1时1分24秒

    if (model.sytime.intValue>0) {
        if (timer == nil) {
            seconds =model.sytime.intValue;
            timer = [NSTimer scheduledTimerWithTimeInterval:1.0f target:self selector:@selector(timerAction:) userInfo:nil repeats:true];
        }
    }
}
//结束
-(void)closeTimer{
    if (timer != nil) {
        [timer invalidate];
    }
}

//定时执行
-(void) timerAction:(NSTimer*)theTimer
{
    
    
    _sytimeLabel.text =[self timeFormatted:seconds];
    seconds--;
    if (seconds == 0) {
        [self closeTimer];
    }
    //打印当前时间
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setDateFormat:@"yyyy-MM-dd HH:mm:ss zzz"];
    NSDate *date = [NSDate date] ;
    NSLog(@"%@",[formatter stringFromDate:date]);
}
//秒 转天：时：分：秒
- (NSString *)timeFormatted:(int)totalSeconds
{
    
    int tseconds = totalSeconds % 60;
    int minutes = (totalSeconds / 60) % 60;
    int hours = (totalSeconds / 3600) % 24;
    int days = (totalSeconds / 3600)/24;
    
    return [NSString stringWithFormat:@"%02d天%02d小时%02d分%02d秒",days,hours, minutes,tseconds];
}