StackOverflow2013

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copied!<p>If you want to group by weekday, the easiest thing to do is to add an attribute such as "weekday" to your entity; then you pass "weekday" as sectionNameKeyPath argument when initializing the NSFetchedResultsController. In this case there is no need to specify a predicate: you will automatically get sections for the weekdays.</p> <p>If you want to group by day, you pass DateAttribute as sectionNameKeyPath argument when initializing the NSFetchedResultsController. Again, there is no need to specify a predicate: you will automatically get sections for the days.</p> <p>What you are trying to do in your code differs from what you asked for. Indeed, you are not trying to get back sections (i.e. grouping by an attribute): you are instead trying to get back a single section for your tableView containing objects described by your entity satisfying a specific predicate, namely the ones whose DateAttribute falls (probably) in the current day. To achieve this, you can use the following code:</p> <pre><code>// start by retrieving day, weekday, month and year components for today NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar]; NSDateComponents *todayComponents = [gregorian components:(NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit) fromDate:[NSDate date]]; NSInteger theDay = [todayComponents day]; NSInteger theMonth = [todayComponents month]; NSInteger theYear = [todayComponents year]; // now build a NSDate object for the input date using these components NSDateComponents *components = [[NSDateComponents alloc] init]; [components setDay:theDay]; [components setMonth:theMonth]; [components setYear:theYear]; NSDate *thisDate = [gregorian dateFromComponents:components]; [components release]; // now build a NSDate object for tomorrow NSDateComponents *offsetComponents = [[NSDateComponents alloc] init]; [offsetComponents setDay:1]; NSDate *nextDate = [gregorian dateByAddingComponents:offsetComponents toDate:thisDate options:0]; [offsetComponents release]; NSDateComponents *tomorrowComponents = [gregorian components:(NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit) fromDate:nextDate]; NSInteger tomorrowDay = [tomorrowComponents day]; NSInteger tomorrowMonth = [tomorrowComponents month]; NSInteger tomorrowYear = [tomorrowComponents year]; [gregorian release]; // now build the predicate needed to fetch the information NSPredicate *predicate = [NSPredicate predicateWithFormat: @"DateAttribute < %@ && DateAttribute > %@", nextDate, thisDate]; </code></pre> <p>This predicate will retrieve exactly all of the objects whose DateAttribute falls within the current day. Hope this helps.</p>

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