CoreData Lightweight Migration + Custom

Question

i'm trying to archive a lightweight migration with some handling after that. I already did the lightweight process and i need some help now handling my entities.

On the old model i used to have an entity "Car" and now i added the entity "Person" with the relationship Person has Cars.

So, after the lightweight migration i need to add a default person "John" and add all cars to him.

Does anyone have some idea?

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

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

    NSError *error = nil;
    _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];

    NSDictionary *options = @{
                              NSMigratePersistentStoresAutomaticallyOption : @YES,
                              NSInferMappingModelAutomaticallyOption : @YES
                              };


    if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:options error:&error]) {
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }

    return _persistentStoreCoordinator;
}

Mundi Mundi · Accepted Answer · 2013-05-09T13:16:01

You can catch if a lightweight migration is going to occur. See this answer for details. There you can set a flag and based on that execute a method after normal startup in which you insert the desired entities.

Notice, though, that lightweight migration should migrate all your existing entities to the new store version, so there is usually no logically compelling reason to use this hook. Instead, you cold just query your (new or old version) store if it contains "John" and his cars and insert them if not.

CoreData Lightweight Migration + Custom

2 Answers