Question

I’m adding repeating events to a Cocoa app I’m working on. I have repeat every day and week fine because I can define these mathematically (3600*24*7 = 1 week). I use the following code to modify the date:

[NSDate dateWithTimeIntervalSinceNow:(3600*24*7*(weeks))] 

I know how many months have passed since the event was repeated but I can’t figure out how to make an NSDate object that represents 1 month/3 months/6 months/9 months into the future. Ideally I want the user to say repeat monthly starting Oct. 14 and it will repeat the 14th of every month.

Answer 1

(Almost the same as this question.)

From the documentation:

Use of NSCalendarDate strongly discouraged. It is not deprecated yet, however it may be in the next major OS release after Mac OS X v10.5. For calendrical calculations, you should use suitable combinations of NSCalendar, NSDate, and NSDateComponents, as described in Calendars in Dates and Times Programming Topics for Cocoa.

Following that advice:

NSDate *today = [NSDate date];  NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];  NSDateComponents *components = [[NSDateComponents alloc] init]; components.month = 1; NSDate *nextMonth = [gregorian dateByAddingComponents:components toDate:today options:0]; [components release];  NSDateComponents *nextMonthComponents = [gregorian components:NSYearCalendarUnit | NSMonthCalendarUnit fromDate:nextMonth];  NSDateComponents *todayDayComponents = [gregorian components:NSDayCalendarUnit fromDate:today];  nextMonthComponents.day = todayDayComponents.day; NSDate *nextMonthDay = [gregorian dateFromComponents:nextMonthComponents];  [gregorian release]; 

There may be a more direct or efficient implementation, but this should be accurate and should point in the right direction.