Question

I have been trying like hell to figure out how to establish a connection between my Core Data & my SQL database. The database isn’t pre-populated, but it will be used amongst many different users when it’s launched.

I have gone through the Core Data & iCloud classes provided by Stanford three times to no avail. I have also looked throughly into SQLite/SQL relational databases in iOS to no avail. The only other option I have is to come on here, post all the code I can, and pray that somebody will have an answer for me. So here it goes…

AppDelegate.m

- (void)saveContext
{
    NSError *error = nil;
    NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
    if (managedObjectContext != nil) {
        if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error]) {

            NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
            abort();
        }
    }
}

#pragma mark - Core Data stack

- (NSManagedObjectContext *)managedObjectContext
{
    if (_managedObjectContext != nil) {
        return _managedObjectContext;
    }

    NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
    if (coordinator != nil) {
        _managedObjectContext = [[NSManagedObjectContext alloc] init];
        [_managedObjectContext setPersistentStoreCoordinator:coordinator];
    }
    return _managedObjectContext;
}

- (NSManagedObjectModel *)managedObjectModel
{
    if (_managedObjectModel != nil) {
        return _managedObjectModel;
    }
    NSURL *modelURL = [self applicationDocumentsDirectory];
    _managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
    return _managedObjectModel;
}

- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
    if (_persistentStoreCoordinator != nil) {
        return _persistentStoreCoordinator;
    }

    NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"shindy.sqlite"];

    NSError *error = nil;
    _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
    if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {

        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }

    return _persistentStoreCoordinator;
}

#pragma mark - Application's Documents directory

- (NSURL *)applicationDocumentsDirectory
{
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *path = [documentsDirectory stringByAppendingPathComponent:@"shindy.sqlite"];

    return [NSURL fileURLWithPath:path];
}

HomeViewController.m

- (void)setupFetchedResultsController
{
    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Shindy"];
    request.sortDescriptors = [NSArray arrayWithObjects:
                               [NSSortDescriptor sortDescriptorWithKey:@"name" ascending:YES],
                               [NSSortDescriptor sortDescriptorWithKey:@"dateAndTime" ascending:YES],
                               [NSSortDescriptor sortDescriptorWithKey:@"photo" ascending:YES],
                               [NSSortDescriptor sortDescriptorWithKey:@"details" ascending:YES],
                               [NSSortDescriptor sortDescriptorWithKey:@"timePosted" ascending:YES],
                               [NSSortDescriptor sortDescriptorWithKey:@"location" ascending:YES],
                                                                                                    nil];

    self.fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:request
                                                                        managedObjectContext:self.shindyDatabase.managedObjectContext
                                                                          sectionNameKeyPath:nil
                                                                                   cacheName:nil];

}

- (void)fetchShindyDataIntoDocument:(UIManagedDocument *)document
{
    dispatch_queue_t fetchQ = dispatch_queue_create("Shindy Fetcher", nil);
    dispatch_async(fetchQ, ^{
        NSArray *shindys = [[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask];
        NSLog(@"shindys = %@", shindys);
        [document.managedObjectContext performBlock:^{
            for (NSDictionary *shindyInfo in shindys) {
                [Shindy shindyWithShindyDBInfo:shindyInfo inManagedObjectContext:document.managedObjectContext];
                NSLog(@"fire");
            }
        }];
    });
}

- (void)useDocument
{
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *path = [documentsDirectory stringByAppendingPathComponent:@"shindy.sqlite"];

    if (![[NSFileManager defaultManager] contentsOfDirectoryAtPath:path error:nil]) {
        [self.shindyDatabase saveToURL:self.shindyDatabase.fileURL forSaveOperation:UIDocumentSaveForCreating completionHandler:^(BOOL success) {
            [self setupFetchedResultsController];
            [self fetchShindyDataIntoDocument:self.shindyDatabase];
        }];
    } else if (self.shindyDatabase.documentState == UIDocumentStateClosed) {
            [self.shindyDatabase openWithCompletionHandler:^(BOOL success) {
        [self setupFetchedResultsController];
        }];
    } else if (self.shindyDatabase.documentState == UIDocumentStateNormal) {
        [self setupFetchedResultsController];
    }
}

- (void)setShindyDatabase:(UIManagedDocument *)shindyDatabase
{
    [self useDocument];
}

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];

    [self fetchShindyDataIntoDocument:self.shindyDatabase];

    if (!self.shindyDatabase) {
        [self setShindyDatabase:self.shindyDatabase];
    }
}

Shindy+ShindyDB.m

+ (Shindy *)shindyWithShindyDBInfo:(NSDictionary *)shindyInfo
            inManagedObjectContext:(NSManagedObjectContext *)context
{
    Shindy *shindy = nil;

    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Shindy"];

    NSSortDescriptor *dateAndTimeSort = [NSSortDescriptor sortDescriptorWithKey:@"dateAndTime" ascending:YES];
    NSSortDescriptor *detailsSort = [NSSortDescriptor sortDescriptorWithKey:@"details" ascending:YES];
    NSSortDescriptor *locationSort = [NSSortDescriptor sortDescriptorWithKey:@"location" ascending:YES];
    NSSortDescriptor *nameSort = [NSSortDescriptor sortDescriptorWithKey:@"name" ascending:YES];
    NSSortDescriptor *photoSort = [NSSortDescriptor sortDescriptorWithKey:@"photo" ascending:YES];
    NSSortDescriptor *timePostedSort = [NSSortDescriptor sortDescriptorWithKey:@"timePosted" ascending:YES];
    // title
    request.sortDescriptors = [NSArray arrayWithObjects:dateAndTimeSort, detailsSort, locationSort, nameSort, photoSort, timePostedSort, nil];

    NSError *error = nil;
    NSArray *matches = [context executeFetchRequest:request error:&error];

    if (!matches || ([matches count] > 1)) {
        // handle error
    } else if ([matches count] == 0) {
        shindy = [NSEntityDescription insertNewObjectForEntityForName:@"Shindy" inManagedObjectContext:context];

        shindy.dateAndTime = [shindyInfo objectForKey:@"dateAndTime"];
        shindy.details = [shindyInfo objectForKey:@"details"];
        shindy.location = [shindyInfo objectForKey:@"location"];
        shindy.name = [shindyInfo objectForKey:@"name"];
        shindy.photo = [shindyInfo objectForKey:@"photo"];
        shindy.timePosted = [shindyInfo objectForKey:@"timePosted"];
        // title
        // Guestlist? The rest?
        // Use below for reference
        shindy.whoseShindy = [User userWithName:[shindyInfo objectForKey:@"whoseShindy"] inManagedObjectContext:context];
    } else {
        shindy = [matches lastObject];
    }

    shindy = [NSEntityDescription insertNewObjectForEntityForName:@"Shindy" inManagedObjectContext:context];
    shindy.dateAndTime = [shindyInfo objectForKey:@"dateAndTime"];
    shindy.details = [shindyInfo objectForKey:@"details"];
    shindy.location = [shindyInfo objectForKey:@"location"];
    shindy.name = [shindyInfo objectForKey:@"name"];
    shindy.photo = [shindyInfo objectForKey:@"photo"];
    shindy.timePosted = [shindyInfo objectForKey:@"timePosted"];

    return shindy;
}

AddShindyViewController.m

- (void)saveShindyToDatabase
{
    NSArray *shindys = [[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask];
    [self.shindyDatabase.managedObjectContext performBlock:^{
        for (NSDictionary *shindyInfo in shindys) {
            [Shindy shindyWithShindyDBInfo:shindyInfo inManagedObjectContext:self.shindyDatabase.managedObjectContext];

            NSURL *url = [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
            // url = [url URLByAppendingPathComponent:@"Default Shindy Database"];
            self.shindyDatabase = [[UIManagedDocument alloc] initWithFileURL:url];

            [self.shindyDatabase setValue:self.detailView.text forKey:@"details"];

            if (FBSession.activeSession.isOpen) {
                [[FBRequest requestForMe] startWithCompletionHandler:
                    ^(FBRequestConnection *connection, NSDictionary<FBGraphUser> *user, NSError *error) {
                        if (!error) {
                            self.name = user.name;
                            self.photo.profileID = user.id;
                            self.username = user.username;
                        }
                    }];
            }
            [self.shindyDatabase setValue:self.name forKey:@"name"];
            [self.shindyDatabase setValue:self.photo forKey:@"photo"];
            [self.shindyDatabase setValue:self.username forKey:@"username"];
            // [Guest guestWithName:self.name username:self.username photo:self.photo inManagedObjectContext:self.shindyDatabase.managedObjectContext];
            [self.shindyDatabase setValue:self.locationManager.location forKey:@"location"];
            [self.shindyDatabase setValue:self.dateAndTimePicker.date forKey:@"dateAndTime"];
        }
    }];
}

I know what I’m asking for is a hell of a lot, but I have exhausted every single resource I have at my disposal. If anybody can even just point me in the right direction, I would be eternally grateful!

Answer 1

If you plan to map an existing database with CoreData you will be unsuccessful.
There’s infact no way you can map any database with CoreData.

Core Data infact is a graph object management, with different storage option, and sqllite is just one of the possibility. At startup, if you choose sqllite as option, your application is going to create a database with a specific tables structure. If you try to connect to a database not created by CoreData framework you will get an error.

What you can do is get rid of CoreData, and build your NSObject to act like entities. But then, you will have to implement all the logic to save, update, versioning, concurrency ecc… and it’s a long (and buggy) way, especially in a multi user environment.

Otherwise, tell me if I misunderstood your question. Maybe, you can post an error stack trace.