iOS计算两个时间的时间差

+ (long)calculteHourL:(NSDate *)endDate startDate:(NSDate *)startDate {

    NSCalendar *cal = [NSCalendar currentCalendar];

    unsigned int unitFlags = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay | NSCalendarUnitHour | NSCalendarUnitMinute | NSCalendarUnitSecond;

    NSDateComponents *d = [cal components:unitFlags fromDate:endDate toDate:startDate options:0];

    long hour = [d hour] + [d minute]/60 + [d second]/3600;

    return hour;

//    int sec = [d hour]*3600 + [d minute]*60 + [d second];

//    NSLog(@"second = %d",[d hour]*3600+[d minute]*60+[d second]);

}