Core Data retrieving relationship data - core-data

Question

I am really having trouble retrieving items that have been created through the Menu entity. This is the code I used to add an item to a specific Menu object
-(void)additem:(NSString *)entity :(NSDictionary *)aDictionary :(NSString *)menu
{
NSLog(#"additem");
NSError *error = nil;
Menu *menuItem = nil;
NSFetchRequest * request = [[NSFetchRequest alloc] init];
[request setEntity:[NSEntityDescription entityForName:#"Menu" inManagedObjectContext:managedObjectContext]];
[request setPredicate:[NSPredicate predicateWithFormat:#"mname=%# and msection =%#",#"Parents",#"Keydates"]];
menuItem = [[managedObjectContext executeFetchRequest:request error:&error] lastObject];
if (error) {
//Handle any errors
}
if (!menuItem) {
//Nothing there to update
NSLog(#"This class doesn't exist");
}
Items *anitem = (Items *)[NSEntityDescription insertNewObjectForEntityForName:#"Items" inManagedObjectContext:managedObjectContext];;
anitem.type = [aDictionary objectForKey:#"type"];
anitem.title = [aDictionary objectForKey:#"title"];
anitem.image = [aDictionary objectForKey:#"image"];
anitem.subtitle = [aDictionary objectForKey:#"subtitle"];
[menuItem addItemsObject:anitem];
[managedObjectContext save:&error];
}
I want to use a predicate to retrieve all the items that were created on a specific Menu object. Here is the code I am trying to retrieve it with.
- (void) readItems: (NSString *)section {
NSLog(#"readItems");
NSError *error = nil;
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Menu"
inManagedObjectContext:managedObjectContext];
fetchRequest.resultType = NSDictionaryResultType;
[fetchRequest setEntity:entity];
[fetchRequest setReturnsObjectsAsFaults:NO];
[fetchRequest setPredicate:[NSPredicate predicateWithFormat:#"mname=%# and msection = %#",#"Parents",#"Keydates"]];
NSArray *fetchedObjects = [managedObjectContext executeFetchRequest:fetchRequest error:&error];
for (Items *item in fetchedObjects) {
NSLog(#">>>>>>%#",item);
}
}
Can anyone point me in the right direction.I know I pass section and don't use it. I have place the actual values in.

Answer 1

Your readItems: method specifies the entity for your fetch as Menu yet when you execute the fetch you are expecting Item (since you start iterating through fetchedObjects and casting them as Item).
Instead what you want to do is et your entity to Item and change the predicate to
[fetchRequest setPredicate:[NSPredicate predicateWithFormat:#"items.mname=%# and items.msection = %#",#"Parents",#"Keydates"]];
Furthermore you should consider renaming your relationships. The relationship field specifies exactly what you would expect to see when you follow the arrow. Thus when I look at Items and follow its arrow to Menu I would expect the name of this relationship to be menu yet you call it menuItems. You have done this correctly for the relationship from Menu to Item.
That way we would end up with a more readable predicate looking like:
[fetchRequest setPredicate:[NSPredicate predicateWithFormat:#"menu.mname=%# and menu.msection = %#",#"Parents",#"Keydates"]];
Happy Coding