私のiOSプロジェクトでは、2つのエンティティ(CoreData)を使用しています。PersonとGifts with To-Many Relationship
私は一人への贈り物の合計を計算する方法を知っています:
NSDecimalNumber *orderSum=[person.gifts valueForKeyPath:@"@sum.priceOfGift"];
しかし、どうすればすべての人の合計を計算できますか?
-(NSFetchedResultsController *) fetchedResultsController {
if (_fetchedResultsController != nil) {
return _fetchedResultsController;
}
//NSError *error = nil;
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Person"
inManagedObjectContext:[self managedObjectContext]];
[fetchRequest setEntity:entity];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"nameOfPerson"
ascending:YES];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[fetchRequest setSortDescriptors:sortDescriptors];
_fetchedResultsController = [[NSFetchedResultsController alloc]initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:@"nameOfGroup" cacheName:nil];
_fetchedResultsController.delegate = self;
return _fetchedResultsController;
}