A propos de "to-many" et prédicat

Question

J'ai deux entités "à plusieurs" relation

Maintenant, je veux aller chercher toutes les catégories qui a seulement favoris (isFavorite) Recettes.

Cela ressemble à:

SELECT c.* 
FROM zcategories c, zrecipes r 
where 
    r.zisfavorite = 1 
    and r.zincategory = c.z_pk 
group by c.zname; 

J'ai essayé

- (NSFetchedResultsController *)fetchedResultsController 
{ 
    if (__fetchedResultsController != nil) { 
     return __fetchedResultsController; 
    } 

    AppDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate]; 
    self.checkedMOC = appDelegate.managedObjectContext; 

    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; 
    // Edit the entity name as appropriate. 
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Categories" inManagedObjectContext:self.checkedMOC]; 
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"ALL recipes.isFavorite == %@", [NSNumber numberWithInt:1]]; 
    [fetchRequest setEntity:entity]; 
    [fetchRequest setPredicate:predicate]; 

    // Set the batch size to a suitable number. 
    [fetchRequest setFetchBatchSize:20]; 

    // Edit the sort key as appropriate. 
    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES]; 
    NSArray *sortDescriptors = [NSArray arrayWithObjects:sortDescriptor, nil]; 

    [fetchRequest setSortDescriptors:sortDescriptors]; 

    // Edit the section name key path and cache name if appropriate. 
    // nil for section name key path means "no sections". 
    NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.checkedMOC sectionNameKeyPath:nil cacheName:@"Master"]; 
    aFetchedResultsController.delegate = self; 
    self.fetchedResultsController = aFetchedResultsController; 

    NSError *error = nil; 
    if (![self.fetchedResultsController performFetch:&error]) { 
     // Replace this implementation with code to handle the error appropriately. 
     // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. 
     NSLog(@"Unresolved error %@, %@", error, [error userInfo]); 
     abort(); 
    } 

    return __fetchedResultsController; 
} 

mais l'erreur se produit 'à plusieurs clés pas autorisés ici'

Answer 1

Si vous voulez que les instances de catégorie que avoir une ou plusieurs recettes qui sont des favoris, essayez le ANY mot-clé

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"ANY recipes.isFavorite == %@", [NSNumber numberWithInt:1]]; 

Si vous voulez que les instances de catégorie qui ont seulement des recettes qui sont les favoris, vous pouvez utiliser le mot-clé ALL:

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"ALL recipes.isFavorite == %@", [NSNumber numberWithInt:1]];