可以使用两个单独的SQLite数据库？ [英] Possible to use two separate SQLite databases?

问题描述

我有一个sqlite数据库，其中存储用户定义的信息和对用户只读的信息。我觉得我可能需要在将来修改只读信息，我不想做一个完整的数据迁移。有没有办法，我可以使用单独的sqlite数据库，它可以轻松替换，只读信息？如果是这样，你能给出一点方向，如何做到这一点？我困惑，因为我目前有所有实体在xcdatamodel - 我会创建两个数据模型？不知道如何工作。提前感谢。

I have one sqlite database in which I store both user-defined information and information which is read-only to the user. I feel like I may need to modify the read-only information in the future, and I don't want to have to do a whole data migration. Is there a way that I can use a separate sqlite database, which can easily be replaced, for the read-only information? If so, can you give a little direction as to how this can be done? I am confused since I currently have all entities on the xcdatamodel - would I create two data models? Not sure how that would work. Thanks in advance.

这不起作用，但请随时提供反馈。

This doesn't work but please feel free to give feedback.

- (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;
}

推荐答案

做的。两个managedObjectModel，两个managedObjectContexts，两个persistentStoreCoordinators，因此，两个持久存储。所有完全分开，这是好的，因为两个商店中的数据之间没有任何关系。这里是kicker为什么sqlite文件创建没有实体和没有数据：在实体甚至得到创建之前，您需要在数据库中执行至少一个获取请求。谁知道？好吧，显然，不是我。无论如何，这对我来说很好，因为我甚至不会有第二个商店准备好，直到应用程序启动后（这是一个额外的功能）。现在，当我的数据文件终于准备好了，我可以只添加sqlite文件，取消注释相关的代码，并将应用程序发送到应用商店。它不会触摸带有用户数据的商店。并且，我将保持我的只读存储在我的捆绑，所以没有迁移。这是怎么回事？

Well, here's what I ended up doing. Two managedObjectModels, two managedObjectContexts, two persistentStoreCoordinators, and hence, two persistent stores. All totally separate, which is fine, since there is no relationship between the data in the two stores at all. And here is the kicker as to why sqlite files get created with no entities and no data at all: before the entities even get created you need to execute at least one fetch request in the db. Who knew? Well, obviously, not me. Anyway, this works well for me, as I won't even have the second store ready until after the app is launched (it is for an additional feature). Now, when my data file is finally ready, I can just add the sqlite file, uncomment the code pertaining to it, and send the app to the app store. It won't touch the store with the user data in it. And, I am going to keep my read-only store in my bundle so no migration. How's that sound?

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