iphone - 可以使用两个单独的 SQLite 数据库吗？

Question

我有一个 sqlite 数据库，其中存储了用户定义的信息和对用户只读的信息。感觉以后可能需要修改只读信息，不想做一个整体的数据迁移。有没有办法可以使用单独的 sqlite 数据库来获取只读信息？如果是这样，您能否就如何做到这一点给出一些指导？我很困惑，因为我目前在 xcdatamodel 上拥有所有实体 - 我会创建两个数据模型吗？不确定那将如何工作。提前致谢。

---

这不起作用，但请随时提供反馈。

- (NSManagedObjectModel *)managedObjectModel {

    NSLog(@"%s", __FUNCTION__);
    if (managedObjectModel != nil) {
        return managedObjectModel;
    }
    //managedObjectModel = [[NSManagedObjectModel mergedModelFromBundles:nil] retain];

    NSString *mainPath = [[NSBundle mainBundle] pathForResource:@"MyApp" ofType:@"mom"];
    NSURL *mainMomURL = [NSURL fileURLWithPath:mainPath];
    managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:mainMomURL];

    [managedObjectModel setEntities:[NSArray arrayWithObjects:
                                          [[managedObjectModel entitiesByName] objectForKey:@"Version"],
                                          [[managedObjectModel entitiesByName] objectForKey:@"Book"],
                                          nil] forConfiguration:@"info"];

    [managedObjectModel setEntities:[NSArray arrayWithObjects:
                                          [[managedObjectModel entitiesByName] objectForKey:@"Settings"],
                                          [[managedObjectModel entitiesByName] objectForKey:@"Persons"],
                                          nil] forConfiguration:@"main"];

    return managedObjectModel;
}

和

- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {

    NSLog(@"%s", __FUNCTION__);
    if (persistentStoreCoordinator != nil) {
        return persistentStoreCoordinator;
    }

    NSString *storePath = [[self applicationDocumentsDirectory] stringByAppendingPathComponent: @"Main.sqlite"];

    NSFileManager *fileManager = [NSFileManager defaultManager];
    if (![fileManager fileExistsAtPath:storePath]) {
        NSString *defaultStorePath = [[NSBundle mainBundle] pathForResource:@"Default" ofType:@"sqlite"];
        if (defaultStorePath) {
            [fileManager copyItemAtPath:defaultStorePath toPath:storePath error:NULL];
        }
    }

    NSURL *storeUrl = [NSURL fileURLWithPath:storePath];
    NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption, [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];    


    NSString *infoStorePath = [[self applicationDocumentsDirectory] stringByAppendingPathComponent: @"Info.sqlite"];
    if (![fileManager fileExistsAtPath:infoStorePath]) {
        NSString *defaultInfoStorePath = [[NSBundle mainBundle] pathForResource:@"DefaultInfo" ofType:@"sqlite"];
        if (defaultInfoStorePath) {
            [fileManager copyItemAtPath:defaultInfoStorePath toPath:infoStorePath error:NULL];
        }
    }

    NSURL *infoStoreUrl = [NSURL fileURLWithPath:infoStorePath];

    persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel: [self managedObjectModel]];
    //persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] init]; 

    NSPersistentStore *mainStore = [persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:@"main" URL:storeUrl options:options error:&error];
    NSPersistentStore *infoStore = [persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:@"verses" URL:infoStoreUrl options:options error:&error];

    NSManagedObject *settingsEntity = [[NSManagedObject alloc] initWithEntity:[[managedObjectModel entitiesByName] objectForKey:@"Settings"] insertIntoManagedObjectContext:self.managedObjectContext];
    [self.managedObjectContext assignObject:settingsEntity toPersistentStore:mainStore];

    NSManagedObject *persons = [[NSManagedObject alloc] initWithEntity:[[managedObjectModel entitiesByName] objectForKey:@"Persons"] insertIntoManagedObjectContext:self.managedObjectContext];
    [self.managedObjectContext persons toPersistentStore:mainStore];

NSManagedObject *version = [[NSManagedObject alloc] initWithEntity:[[managedObjectModel entitiesByName] objectForKey:@"Version"] insertIntoManagedObjectContext:self.managedObjectContext];
[self.managedObjectContext assignObject:version toPersistentStore:infoStore];

NSManagedObject *book = [[NSManagedObject alloc] initWithEntity:[[managedObjectModel entitiesByName] objectForKey:@"Book"] insertIntoManagedObjectContext:self.managedObjectContext];
[self.managedObjectContext assignObject:book toPersistentStore:infoStore];

和

- (NSManagedObjectContext *)managedObjectContext {

    NSLog(@"%s", __FUNCTION__);
    if (managedObjectContext != nil) {
        return managedObjectContext;
    }

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

Answer 1

来自文档的部分答案:

http://developer.apple.com/library/ios/#documentation/cocoa/Conceptual/CoreData/Articles/cdMOM.html

Configurations

A configuration has a name and an associated set of entities. The sets may overlap—that is, a given entity may appear in more than one configuration. You establish configurations programmatically using setEntities:forConfiguration: or using the Xcode data modeling tool (see Xcode Tools for Core Data), and retrieve the entities for a given configuration name using entitiesForConfiguration:.

You typically use configurations if you want to store different entities in different stores. A persistent store coordinator can only have one managed object model, so by default each store associated with a given coordinator must contain the same entities. To work around this restriction, you can create a model that contains the union of all the entities you want to use. You then create configurations in the model for each of the subsets of entities that you want to use. You can then use this model when you create a coordinator. When you add stores, you specify the different store attributes by configuration. When you are creating your configurations, though, remember that you cannot create cross-store relationships.

然后 NSPersistentStoreCoordinator 允许您创建多个存储，每个存储具有不同的配置。

任何人都有如何执行所有这些操作的示例？