how can I improve this "DateFromNextWeekDay:FromDate" method code?

Question

Would be happy to hear of suggestions re how to improve / shorten this method. In short needing to:

Find the next date for which it's day of week (e.g. Wed) matches what is passed into the method.
For example the next WED from a given date (and including that given date)

Code Below:

- (NSDate*)DateFromNextWeekDay:(NSInteger)weekDay FromDate:(NSDate*)fromDate {
    // Returns the next week day, as specified by "weekDay", from the specified "fromDate" 
    NSDate *fromDateMidday = [[NSDate date] dateBySettingHour:12 andMinute:0];
    NSDate *dateCounter  = [[fromDateMidday copy] dateByAddingTimeInterval:-86400];     // Take 1 day away, which will get incremented in the loop
    NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    NSInteger day;
    do{
        dateCounter  = [dateCounter dateByAddingTimeInterval:86400];
        unsigned units = NSWeekdayCalendarUnit;
        NSDateComponents *components = [gregorian components:units fromDate:dateCounter];
        day = [components weekday];
    } while(day != weekDay);
    [gregorian release];
    return dateCounter;
}

thanks

drewag · Accepted Answer · 2011-03-21T01:09:35.080

3

You could just find the day of the week of the passed in date, subtract that from the target day of the week, and finally add that result to the date passed in. No need to loop through the dates. So it would be:

daysToAdd = ( targetDayOfWeek - currentDayDayOfWeek ) % 7

The reason for moding the subtraction is to handle the cases where the target day is smaller than the current day (it is a saturday and you are looking for a tuesday for example).

edited Mar 21 '11 at 01:09

answered Mar 21 '11 at 00:51

drewag

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oh wow - I didn't realize you could add/subtract dates like that! – Greg Mar 21 '11 at 00:55
so the resultant "nextDate" itself would retain the time (i.e. hour/minute) from the original "currentDate" correct? And you would still need to calculate currentDay using NSDateComponents correct? – Greg Mar 21 '11 at 00:57
@greg You won't be added the date objects themselves. You will use the same technique you are currently using ( setting up the NSDateComponents and then using the weekday attribute ) to get the NSInteger representation of the day of the week. Then you can do the math, and finally add that number of days back to the original date. – drewag Mar 21 '11 at 00:57

how can I improve this "DateFromNextWeekDay:FromDate" method code?

1 Answers1