多个NSPersistentStoreCoordinator实例可以连接到同一个底层SQLite持久性存储吗？

Question

Everything I've read about using Core Data on multiple threads talks about using multiple NSManagedObjectContext instances sharing a single NSPersistentStoreCoordinator . This is understood and I've made it work in an app that uses Core Data on the main thread in support of the UI and has a background fetch operation that can take a while to run.

The problem is that access to the underlying SQLite persistent store is serialized by the NSPersistentStoreCoordinator , so there are still occasions where the UI is blocked by the background fetch operation.

The background fetch operation will never update the data, only read from it. Can I set up an entirely parallel Core Data stack ( NSManagedObjectContext , NSManagedPersistentStoreCoordinator , and NSManagedObjectModel ) on the background thread connected to the same underlying SQLite persistent store? It seems like this would give complete concurrency between the UI thread and the background fetch operation.

Answer 1

My own tentative answer to this is now yes .

I initialize my background operation by passing it the NSPersistentStore instance. On the background thread, the properties of this store, including the URL, are used to create a whole new Core Data stack like this:

    //  create managed object model
    NSURL *modelUrl = [[NSBundle bundleForClass:[self class]] URLForResource:@"..." withExtension:@"..."];
    NSManagedObjectModel *managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelUrl];

    //  create persistent store coordinator
    NSPersistentStoreCoordinator *persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:managedObjectModel];
    NSError *error = nil;
    [persistentStoreCoordinator addPersistentStoreWithType:[store type]
                                            configuration:[store configurationName]
                                                      URL:[store URL]
                                                   options:[store options]
                                                     error:&error];

    //  create managed object context
    NSManagedObjectContext *context = [[NSManagedObjectContext alloc] init];
    [context setPersistentStoreCoordinator:persistentStoreCoordinator];
    [persistentStoreCoordinator release];
    [managedObjectModel release];

I then perform the background fetch using this newly created NSManagedObjectContext instance.

Everything seems to work just fine. I'm not yet accepting my own answer, though, as I would love to have someone provide supporting or contradicting evidence to my findings.