Calculating certain NSDates from days of weeks/weeks of years

Question

Is there an easy way to calculate dates according to a criteria with NSCalendar and/or NSCalendarComponents? I've been looking at the documentation for a while but it seems a bit complicated. For example, I need "Wednesday 6:00pm"s for the next 15 even-numbered weeks (including this one if it's even numbered and not past that date/time yet.)

Answer 1

I ended up answering my own question. It's really easy when you know -[NSCalendar dateBySettingUnit:value:ofDate:options:] auto-increments forward to the next matching date.

NSCalendar *calendar = [NSCalendar calendarWithIdentifier:NSCalendarIdentifierISO8601];

NSDate *date = [NSDate date];

// find the next Wednesday 6 o'clock
date = [calendar dateBySettingUnit:NSCalendarUnitSecond value:0 ofDate:date options:0];
date = [calendar dateBySettingUnit:NSCalendarUnitMinute value:0 ofDate:date options:0];
date = [calendar dateBySettingUnit:NSCalendarUnitHour value:18 ofDate:date options:0];
date = [calendar dateBySettingUnit:NSCalendarUnitWeekday value:4 ofDate:date options:0];

// skip one week if it's not an even week
NSDateComponents *components = [calendar components:NSCalendarUnitWeekOfYear fromDate:date];
date = [calendar dateByAddingUnit:NSCalendarUnitWeekOfYear value:components.weekOfYear % 2 toDate:date options:0];

// 15 weeks of this
for (int i = 0; i < 15; i++)
{
    NSDate *testDate = [calendar dateByAddingUnit:NSCalendarUnitWeekOfYear value:i * 2 toDate:date options:0];
    NSLog(@"Date: %@", testDate);
}