iOS 獲取指定日期的時間（年、月、日、星期、時、分、秒等）

1、注意：weekday中1表示週日，2表示週一，7表示週六。

    NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierGregorian];
    
    NSInteger unitFlags = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitWeekday | NSCalendarUnitDay | NSCalendarUnitHour | NSCalendarUnitMinute | NSCalendarUnitSecond;
    
    NSDateComponents *comps = [calendar components:unitFlags fromDate:[NSDate date]];

NSLog(@"year = %ld, month = %ld, weekday = %ld, day = %ld, hour = %ld, minure = %ld, second = %ld",
          comps.year,comps.month,comps.weekday,comps.day,comps.hour,comps.minute,comps.second);

如果還想獲取其它時間信息，可以繼續在  unitFlags 中添加類別（如：NSCalendarUnitTimeZone)