从NSDate中分别分离提取出年月日分时秒的方法

NSDate *now = [NSDate date];
NSCalendar *cal = [NSCalendar currentCalendar];
        unsigned int unitFlags = NSWeekdayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit;
        NSDateComponents *dd = [cal components:unitFlags fromDate:now];
        int week = [dd weekday];
        int hour = [dd hour];
        int minute = [dd minute];
        second = [dd second];

That is it！