Opens up a Core Data store using a custom atomic type and migrates the store to another type. This would be useful for importing data, e.g for opening up a CSV file using a custom type and converting it an SQLite store. However, while this is easy and makes use of in-house components, it introduces more steps than are necessary for importing dat…

MigrateCoreDataStoreType.m

// grab the model:
NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"StoreMigration" withExtension:@"momd"];
NSManagedObjectModel *managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];

// create a new example store type:
NSPersistentStoreCoordinator *csvCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:managedObjectModel];
csvCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:managedObjectModel];
if (![csvCoordinator addPersistentStoreWithType:[SMGCSVStore type] configuration:nil URL:csvStoreURL options:nil error:&error]) {
    NSLog(@"Couldn't add store: %@", [error localizedDescription]);
    abort();
}

// set up a context and check there are two events:
NSManagedObjectContext *csvContext = [[NSManagedObjectContext alloc] init];
[csvContext setPersistentStoreCoordinator:csvCoordinator];
NSFetchRequest *csvRequest = [[NSFetchRequest alloc] initWithEntityName:@"SMGEvent"];
NSArray *csvEvents = [csvContext executeFetchRequest:csvRequest error:&error];
if (csvEvents) {
    NSLog(@"Loading from CSV store:");
    for (NSManagedObject *event in csvEvents) {
        NSLog(@"Event date: %@", [event valueForKey:@"date"]);
    }
} else {
    NSLog(@"Couldn't retrieve events: %@", [error localizedDescription]);
    abort();
}

// try to migrate the CSV store over to SQLite:
NSPersistentStore *csvStore = [csvCoordinator persistentStoreForURL:csvStoreURL];
if (![csvCoordinator migratePersistentStore:csvStore toURL:sqlStoreURL options:nil withType:NSSQLiteStoreType error:&error]) {
    NSLog(@"Failed to migrate: %@", [error localizedDescription]);
    abort();
}

// save the new store to disk:
if (![csvContext save:&error]) {
    NSLog(@"Failed to save: %@", [error localizedDescription]);
    abort();
}

// load up the store directly from the migrated SQLite store:
NSPersistentStoreCoordinator *sqlCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:managedObjectModel];
if (![sqlCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:sqlStoreURL options:nil error:&error]) {
    NSLog(@"Couldn't add store: %@", [error localizedDescription]);
    abort();
}

// check it has two events:
NSManagedObjectContext *sqlContext = [[NSManagedObjectContext alloc] init];
[sqlContext setPersistentStoreCoordinator:sqlCoordinator];
NSFetchRequest *sqlRequest = [[NSFetchRequest alloc] initWithEntityName:@"SMGEvent"];
NSArray *sqlEvents = [sqlContext executeFetchRequest:sqlRequest error:&error];
if (sqlEvents) {
    NSLog(@"Loading from SQL store:");
    for (NSManagedObject *event in sqlEvents) {
        NSLog(@"Event date: %@", [event valueForKey:@"date"]);
    }
} else {
    NSLog(@"Couldn't retrieve events: %@", [error localizedDescription]);
    abort();
}