Question

I have two objects set in the following relationship:

News <->> Link

Link contains two attributes where one is a URL and the other is some associated text. I initially created News and populate it with information:

NSManagedObject *newsData = [NSEntityDescription
                                         insertNewObjectForEntityForName:@"News"
                                         inManagedObjectContext:context];
        [newsData setValue:[object objectForKey:@"username"] forKey:@"username"];
        [newsData setValue:message forKey:@"content"];
        [newsData setValue:[object objectForKey:@"when"] forKey:@"date"];
        [newsData setValue:imgUrl forKey:@"img"];

        NSMutableSet *links = [launchTicker mutableSetValueForKey:@"links"];

Then inside a for loop, I create a Link:

NSManagedObject *linkInfo = [NSEntityDescription
                                                          insertNewObjectForEntityForName:@"Link"
                                                          inManagedObjectContext:context];
                    [linkInfo setValue:[object objectForKey:@"id"] forKey:@"id"];
                    [linkInfo setValue:[[item firstChild] content] forKey:@"text"];
                    [linkInfo setValue:[[item attributes] valueForKey:@"href"] forKey:@"url"];
                    [links addObject:linkInfo];

After the for loop is done, I put the set of Link of I created to the News object:

[newsData setValue:links forKey:@"links"];

When I’m fetching for the data, I can fetch the information for News just fine, but when I fetch for the Link, I get nothing back:

for (NSManagedObject *info in fetchedObjects) {

    [fetchRequest setReturnsObjectsAsFaults:NO];
    [fetchRequest setRelationshipKeyPathsForPrefetching:[NSArray arrayWithObjects:@"links", nil]];

    NSMutableArray *url = [[NSMutableArray alloc] init];
    NSMutableArray *text = [[NSMutableArray alloc] init];

    NSSet* links = [info valueForKey:@"links"];
    NSArray *arrayLinks = [links allObjects];

    for(NSManagedObject *link in arrayLinks) {
        [url addObject:[link valueForKeyPath:@"url"]];
        [text addObject:[link valueForKeyPath:@"text"]];
    }

Can anyone please give their insight on why I’m getting back 0 objects when I try to access my related objects?

Answer 1

I solved it with the following code:

NSEntityDescription *linkEntity = [NSEntityDescription entityForName:@"Link"inManagedObjectContext:context]; 
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"ANY id == %@", [info valueForKey:@"id"]]; 
[fetchRequest setEntity:linkEntity]; 
[fetchRequest setPredicate:predicate]; 
NSArray *results = [context executeFetchRequest:fetchRequest error:&error];