Why is the class wrong for NSFetchRequest?

Question

Hello,

I am working with an undocumented API (Osirix) and I have a sister-question to the one I posted here.

I am having trouble loading objects from a managed object context.

With loading from API, using their instance of _context and _model

2010-05-28 14:05:13.588 OsiriX[44012:a0f] Entity: Study
2010-05-28 14:05:13.589 OsiriX[44012:a0f] EntityClassName: DicomStudy
2010-05-28 14:05:13.589 OsiriX[44012:a0f] ClassName: DicomStudy

With loading from Fetch Request (and my own instance of _context, and _model)

2010-05-28 14:19:09.956 rcOsirix[44431:7a03] Entity: Study
2010-05-28 14:19:09.957 rcOsirix[44431:7a03] EntityClassName: DicomStudy
2010-05-28 14:19:09.958 rcOsirix[44431:7a03] ClassName: NSManagedObject

output given by:

NSLog(@"Entity: %@",[[item entity] name]);
NSLog(@"EntityClassName: %@", [[item entity] managedObjectClassName]);
NSLog(@"ClassName: %s", class_getName(object_getClass([item class])));

So it is obvious that even though the Entity thinks it is a DicomSeries - it is not. It is just a NSManagedObject. DicomSeries has some "hard-coded" KVC stuff that I ran into a problem with in my other question.

I'm pursuing a different line of reasoning in this thread - with the loading of the objects.

The following is their code:

- (NSManagedObjectModel *)managedObjectModel
{
    if (managedObjectModel) return managedObjectModel;

    NSMutableSet *allBundles = [[NSMutableSet alloc] init];
    [allBundles addObject: [NSBundle mainBundle]];
    [allBundles addObjectsFromArray: [NSBundle allFrameworks]];

    managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL: [NSURL fileURLWithPath: [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"/OsiriXDB_DataModel.mom"]]];
    [allBundles release];

    return managedObjectModel;
}

- (NSManagedObjectContext *) managedObjectContextLoadIfNecessary:(BOOL) loadIfNecessary
{
    NSError *error = nil;
    NSString *localizedDescription;
    NSFileManager *fileManager;

    if( currentDatabasePath == nil)
        return nil;

    if (managedObjectContext)
        return managedObjectContext;

    if( loadIfNecessary == NO) return nil;

    fileManager = [NSFileManager defaultManager];

    [persistentStoreCoordinator release];

    persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel: self.managedObjectModel];

    managedObjectContext = [[NSManagedObjectContext alloc] init];
    [managedObjectContext setPersistentStoreCoordinator: persistentStoreCoordinator];

    NSURL *url = [NSURL fileURLWithPath: currentDatabasePath];

    if (![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:url options:nil error:&error])
    {
        NSLog(@"********** managedObjectContextLoadIfNecessary FAILED: %@", error);
        localizedDescription = [error localizedDescription];
        error = [NSError errorWithDomain:@"OsiriXDomain" code:0 userInfo:[NSDictionary dictionaryWithObjectsAndKeys:error, NSUnderlyingErrorKey, [NSString stringWithFormat:@"Store Configuration Failure: %@", ((localizedDescription != nil) ? localizedDescription : @"Unknown Error")], NSLocalizedDescriptionKey, nil]];
    }

    [[managedObjectContext undoManager] setLevelsOfUndo: 1];
    [[managedObjectContext undoManager] disableUndoRegistration];

    // This line is very important, if there is NO database.sql file
    [self saveDatabase: currentDatabasePath];

    return managedObjectContext;
}

This is my code:

NSManagedObjectModel* DataModule::managedObjectModel()
{
if (_managedObjectModel) return _managedObjectModel;

    NSMutableSet *allBundles = [[NSMutableSet alloc] init];
    [allBundles addObject: [NSBundle mainBundle]];
    [allBundles addObjectsFromArray: [NSBundle allFrameworks]];

_managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL: [NSURL fileURLWithPath: [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"/OsiriXDB_DataModel.mom"]]];

    [allBundles release];

return [_managedObjectModel retain];
}

...
        NSError *error = nil;
        [_storeCoordinator release];

        _storeCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel: managedObjectModel()];

        _context = [[NSManagedObjectContext alloc] init];
        [_context setPersistentStoreCoordinator: _storeCoordinator];

        NSURL *url = [NSURL fileURLWithPath: [[NSString alloc] initWithCString:_DBPath.c_str()]];

        if (url == nil) { [pool release]; _loadLock = false; return nil; }

        if (![_storeCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:url options:nil error:&error])
        {
            NSLog(@"********** managedObjectContextLoadIfNecessary FAILED: %@", error);
            NSString *localizedDescription = [error localizedDescription];
            error = [NSError errorWithDomain:@"OsiriXDomain" code:0 userInfo:[NSDictionary dictionaryWithObjectsAndKeys:error, NSUnderlyingErrorKey, [NSString stringWithFormat:@"Store Configuration Failure: %@", ((localizedDescription != nil) ? localizedDescription : @"Unknown Error")], NSLocalizedDescriptionKey, nil]];

            //Exit Failure
            [pool release]; _loadLock = false; return nil;
        }

        [[_context undoManager] setLevelsOfUndo: 1];
        [[_context undoManager] disableUndoRegistration];
...

I am including all the same frameworks.... but _allBundles isn't even used to create the managedObjectModel so I don't know what it's supposed to do except load them into memory so that the mom can look at them while loading.

Totally lost.

Help!

Why would objects returned by my FetchRequest with the same Entity come out as NSManagedObjects and not DicomStudys? I'm including DicomStudy.h so it should see the object during creation of the model, context, and fetch request.

[request setEntity: [[managedObjectModel() entitiesByName] objectForKey:@"Study"]];

Thanks in advance,

-Stephen

Answer 1

First question, in your model, are you telling Core Data to use your DicomStudy subclass or is it set to NSManagedObject still (the default)?

Update

Ok, next, change the third line of logging to the following:

NSLog(@"ClassName: %@", [item class]);

And show the output.

Answer 2

Hooookay,

I feel like a gargantuan turd for answering every single one of my questions, but oh well.

So, the answer is that the Framework I was including had no compiled source. BenT over on the Apple Dev Forums mentioned that the source needed to be compiled... so I looked into the Framework I was importing at it appears that it only copies the header files, and does not compile anything.

This was done (I think, since I've gotten no reply from the dev's of that Framework) because the framework was intended to be used as part of a plug-in for the main software. Since the plug-in architecture loads all the compiled classes, having just the headers in the Framework prevented the objc[1378]: Class BLAH is implemented in both X and Y. One of the two will be used. Which one is undefined. "fun-time" errors.

So, it looks like I'll have to either include the source or make a new framework from their source.

Thanks to Marcus for helping me out. I was hoping this wasn't just a "RTFM" problem since I've only ben dev'ing for the Apple platform since Nov of 2009. I hadn't gotten around to learning CoreData yet...

-Stephen