Tricking Core Data Into Performing Progressive Migrations

cd_progressive_migration.m

+ (BOOL)migrateStoreAtURL:(NSURL *)storeURL
             	   models:(NSArray<NSManagedObjectModel *> *)moms // @[ mom_v1, mom_v2, mom_v3 ... ];
                    error:(NSError **)error {
    // Find an index of the current store's mom
    NSDictionary *meta = [NSPersistentStoreCoordinator metadataForPersistentStoreOfType:NSSQLiteStoreType URL:storeURL error:error];
    if (!meta) {
        return NO;
    }
    NSInteger idx = [moms indexOfObjectPassingTest:^BOOL(NSManagedObjectModel * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        return [obj isConfiguration:nil compatibleWithStoreMetadata:meta];
    }];
    if (idx == NSNotFound) {
        return NO;
    }

    // Progressively migrate between moms until final mom is reached
    while (idx < (moms.count - 1)) {
        @autoreleasepool {
            NSManagedObjectModel *mom = moms[idx+1];
            NSPersistentStoreCoordinator *psc = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:mom];
            if (![psc addPersistentStoreWithType:NSSQLiteStoreType
                                   configuration:nil
                                             URL:storeURL
                                         options:@{ NSMigratePersistentStoresAutomaticallyOption : @YES,
                                                    NSInferMappingModelAutomaticallyOption : @YES }
                                           error:error]) {
                return NO;
            }
            idx += 1;
        }
    }

    return YES;
}