得到系统的时间 并转化成NSString NSDate

  //获取时间

    NSDate *date = [[NSDate alloc]init];

    NSDateFormatter *formatter = [[NSDateFormatter alloc]init];

    [formatter setDateFormat:@"HH:mm:ss"];

//    [formatter setDateFormat:@"YYYY-MM-dd-HH-mm-ss"];

    NSString *currentTime = [formatter stringFromDate:date];

    return currentTime;