iOS 11+ 如何将现有核心数据迁移到共享应用组以用于扩展？

Question

当我使用核心数据模板创建 iOS 11 应用程序时，它会在 AppDelete.m 中自动生成以下代码。

synthesize persistentContainer = _persistentContainer;

- (NSPersistentContainer *)persistentContainer {
    // The persistent container for the application. This implementation creates and returns a container, having loaded the store for the application to it.
    @synchronized (self) {
        if (_persistentContainer == nil) {
            _persistentContainer = [[NSPersistentContainer alloc] initWithName:@"My_History"];
            [_persistentContainer loadPersistentStoresWithCompletionHandler:^(NSPersistentStoreDescription *storeDescription, NSError *error) {
                if (error != nil) {
                    // Replace this implementation with code to handle the error appropriately.
                    // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.

                    /*
                     Typical reasons for an error here include:
                     * The parent directory does not exist, cannot be created, or disallows writing.
                     * The persistent store is not accessible, due to permissions or data protection when the device is locked.
                     * The device is out of space.
                     * The store could not be migrated to the current model version.
                     Check the error message to determine what the actual problem was.
                    */
                    NSLog(@"Unresolved error %@, %@", error, error.userInfo);
                    abort();
                }
            }];
        }
    }

    return _persistentContainer;
}

- (void)saveContext {
NSManagedObjectContext *context = self.persistentContainer.viewContext;
NSError *error = nil;
if ([context hasChanges] && ![context save:&error]) {
    // Replace this implementation with code to handle the error appropriately.
    // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
    NSLog(@"Unresolved error %@, %@", error, error.userInfo);
    abort();
}

我想添加一个访问核心数据历史记录的 Today 和 iMessage 扩展。 根据我阅读的内容，如果此数据存在，我需要将其迁移到共享应用程序容器中。 我该怎么做？

代码在目标 C 中。

我已经阅读了其他涉及此问题的问题，但所有这些问题似乎都是在 Apple 改变核心数据的工作方式以使其更容易之前。 正如您在我的代码中看到的那样，我从未指定数据存储的确切文件名是什么。 我看到的每个示例都有类似“My_History.sqllite”的内容。 我什至不知道我的是否是 sql lite 数据库，它只是由该代码创建的。

Answer 1

solidsnake4444的回答节省了我的时间。 这是 Swift 5.0 版本。

lazy var persistentContainer: NSPersistentContainer = {
    let container = NSPersistentContainer(name: "MyApp")
    let storeURL = FileManager.default.containerURL(forSecurityApplicationGroupIdentifier: "group.com.my.app")!.appendingPathComponent("MyApp.sqlite")

    var defaultURL: URL?
    if let storeDescription = container.persistentStoreDescriptions.first, let url = storeDescription.url {
        defaultURL = FileManager.default.fileExists(atPath: url.path) ? url : nil
    }

    if defaultURL == nil {
        container.persistentStoreDescriptions = [NSPersistentStoreDescription(url: storeURL)]
    }
    container.loadPersistentStores(completionHandler: { [unowned container] (storeDescription, error) in
        if let error = error as NSError? {
            fatalError("Unresolved error \(error), \(error.userInfo)")
        }

        if let url = defaultURL, url.absoluteString != storeURL.absoluteString {
            let coordinator = container.persistentStoreCoordinator
            if let oldStore = coordinator.persistentStore(for: url) {
                do {
                    try coordinator.migratePersistentStore(oldStore, to: storeURL, options: nil, withType: NSSQLiteStoreType)
                } catch {
                    print(error.localizedDescription)
                }

                // delete old store
                let fileCoordinator = NSFileCoordinator(filePresenter: nil)
                fileCoordinator.coordinate(writingItemAt: url, options: .forDeleting, error: nil, byAccessor: { url in
                    do {
                        try FileManager.default.removeItem(at: url)
                    } catch {
                        print(error.localizedDescription)
                    }
                })
            }
        }
    })
    return container
}()

Answer 2

我最终得到它执行以下操作。 sqlite 文件实际上是我的 init 名称加上最后的 .sqlite。

+ (NSPersistentContainer*) GetPersistentContainer {
    //Init the store.
    NSPersistentContainer *_persistentContainer = [[NSPersistentContainer alloc] initWithName:@"Test_App"];

    //Define the store url that is located in the shared group.
    NSURL* storeURL = [[[NSFileManager defaultManager] containerURLForSecurityApplicationGroupIdentifier:@"group.Test_App"] URLByAppendingPathComponent:@"Test_App.sqlite"];

    //Determine if we already have a store saved in the default app location.
    BOOL hasDefaultAppLocation = [[NSFileManager defaultManager] fileExistsAtPath: _persistentContainer.persistentStoreDescriptions[0].URL.path];

    //Check if the store needs migration.
    BOOL storeNeedsMigration = hasDefaultAppLocation && ![_persistentContainer.persistentStoreDescriptions[0].URL.absoluteString isEqualToString:storeURL.absoluteString];

    //Check if the store in the default location does not exist.
    if (!hasDefaultAppLocation) {
        //Create a description to use for the app group store.
        NSPersistentStoreDescription *description = [[NSPersistentStoreDescription alloc] init];

        //set the automatic properties for the store.
        description.shouldMigrateStoreAutomatically = true;
        description.shouldInferMappingModelAutomatically = true;

        //Set the url for the store.
        description.URL = storeURL;

        //Replace the coordinator store description with this description.
        _persistentContainer.persistentStoreDescriptions = [NSArray arrayWithObjects:description, nil];
    }

    //Load the store.
    [_persistentContainer loadPersistentStoresWithCompletionHandler:^(NSPersistentStoreDescription *storeDescription, NSError *error) {
        //Check that we do not have an error.
        if (error == nil) {
            //Check if we need to migrate the store.
            if (storeNeedsMigration) {
                //Create errors to track migration and deleting errors.
                NSError *migrateError;
                NSError *deleteError;

                //Store the old location URL.
                NSURL *oldStoreURL = storeDescription.URL;

                //Get the store we want to migrate.
                NSPersistentStore *store = [_persistentContainer.persistentStoreCoordinator persistentStoreForURL: oldStoreURL];

                //Set the store options.
                NSDictionary *storeOptions = @{ NSSQLitePragmasOption : @{ @"journal_mode" : @"WAL" } };

                //Migrate the store.
                NSPersistentStore *newStore = [_persistentContainer.persistentStoreCoordinator migratePersistentStore: store toURL:storeURL options:storeOptions withType:NSSQLiteStoreType error:&migrateError];

                //Check that the store was migrated.
                if (newStore && !migrateError) {
                    //Remove the old SQLLite database.
                    [[[NSFileCoordinator alloc] init] coordinateWritingItemAtURL: oldStoreURL options: NSFileCoordinatorWritingForDeleting error: &deleteError byAccessor: ^(NSURL *urlForModifying) {
                        //Create a remove error.
                        NSError *removeError;

                        //Delete the file.
                        [[NSFileManager defaultManager] removeItemAtURL: urlForModifying error: &removeError];

                        //If there was an error. Output it.
                        if (removeError) {
                            NSLog(@"%@", [removeError localizedDescription]);
                        }
                    }
                     ];

                    //If there was an error. Output it.
                    if (deleteError) {
                        NSLog(@"%@", [deleteError localizedDescription]);
                    }
                }
            }
        } else {
            // Replace this implementation with code to handle the error appropriately.
            // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.

            /*
             Typical reasons for an error here include:
             * The parent directory does not exist, cannot be created, or disallows writing.
             * The persistent store is not accessible, due to permissions or data protection when the device is locked.
             * The device is out of space.
             * The store could not be migrated to the current model version.
             Check the error message to determine what the actual problem was.
             */
            NSLog(@"Unresolved error %@, %@", error, error.userInfo);
            abort();
        }
    }];

    //Return the container.
    return _persistentContainer;
}

Answer 3

更新：

为了迁移现有的持久化存储， NSPersistentContainer包含了persistentStoreCoordinator ，它是NSPersistentStoreCoordinator的一个实例。 这公开了migratePersistentStore:toURL:options:withType:error:方法来迁移持久存储。

我会做以下事情：

// Get the reference to the persistent store coordinator
let coordinator = persistentContainer.persistentStoreCoordinator
// Get the URL of the persistent store
let oldURL = persistentContainer.persistentStoreDescriptions.url
// Get the URL of the new App Group location
let newURL = NSFileManager.defaultManager().containerURLForSecurityApplicationGroupIdentifier("YOUR_APP_GROUP")
// Get the reference to the current persistent store
let oldStore = coordinator.persistentStore(for: oldURL)
// Migrate the persistent store
do {
   try coordinator.migratePersistentStore(oldStore, to: newURL, options: nil, withType: NSSQLiteStoreType)
} catch {
   // ERROR
}

请注意，以上内容尚未经过测试，并且我没有处理 Optionals，因此它不完整。 另外，我很抱歉它在 Swift 中。 希望你可以很容易地用 Objective-C 编写等价的代码。

原来的：

下面概述了如何创建一个NSPersistentContainer接口到一个非默认位置的持久存储。

NSPersistentContainer公开了defaultDirectoryURL ，并声明：

此方法返回一个依赖于平台的NSURL ，持久存储将位于或当前位于该 NSURL。 可以在NSPersistentContainer的子类中重写此方法。

如果您将NSPersistentContainer子类化并使用containerURLForSecurityApplicationGroupIdentifier将defaultDirectoryURL定义为 App Group 目录，那么您应该能够访问您的应用程序和扩展之间的容器（假设它们具有相同的 App Group 权利）。

NSPersistentContainer还公开了还具有 URL 实例的persistentStoreDescriptions 。 同样，您可以在调用loadPersistentStoresWithCompletionHandler:之前将其更新为 App Group URL。

请注意，我没有使用NSPersistentContainer ，并且不知道这种共享是否会导致任何并发问题。

Answer 4

移动NSPersistentCloudKitContainer时，这对我有用。 有几点需要注意：

• 您需要确保在持久存储描述上设置了cloudKitContainerOptions否则同步将停止工作
• 不要调用migratePersistentStore否则你会得到重复的记录，而是使用replacePersistentStore - 有关更多信息，请参阅此线程
• 成功迁移后，您可能希望删除旧数据库， destroyPersistentStore听起来很有希望，但似乎并没有真正删除文件 - 请参阅此问题

struct PersistenceController {
    static let shared = PersistenceController()

    let container: NSPersistentCloudKitContainer

    init(inMemory: Bool = false) {
        container = NSPersistentCloudKitContainer(name: "MyCuteDB")
        
        if inMemory {
            container.persistentStoreDescriptions.first!.url = URL(fileURLWithPath: "/dev/null")
        } else {
            // Use App Groups so app and extensions can access database
            let sharedStoreURL = FileManager.default.containerURL(forSecurityApplicationGroupIdentifier: "group.com.yourdomain.yourapp")!.appendingPathComponent("\(container.name).sqlite")
            let defaultStoreURL = container.persistentStoreDescriptions.first!.url! //the URL always starts out in the default location

            // move database to shared location if needed
            if FileManager.default.fileExists(atPath: defaultStoreURL.path) && !FileManager.default.fileExists(atPath: sharedStoreURL.path) {
                let coordinator = container.persistentStoreCoordinator
                do {
                    try coordinator.replacePersistentStore(at: sharedStoreURL, destinationOptions: nil, withPersistentStoreFrom: defaultStoreURL, sourceOptions: nil, ofType: NSSQLiteStoreType)
                    try? coordinator.destroyPersistentStore(at: defaultStoreURL, ofType: NSSQLiteStoreType, options: nil)
                    
                    // destroyPersistentStore says it deletes the old store but it actually truncates so we'll manually delete the files
                    NSFileCoordinator(filePresenter: nil).coordinate(writingItemAt: defaultStoreURL.deletingLastPathComponent(), options: .forDeleting, error: nil, byAccessor: { url in
                        try? FileManager.default.removeItem(at: defaultStoreURL)
                        try? FileManager.default.removeItem(at: defaultStoreURL.deletingLastPathComponent().appendingPathComponent("\(container.name).sqlite-shm"))
                        try? FileManager.default.removeItem(at: defaultStoreURL.deletingLastPathComponent().appendingPathComponent("\(container.name).sqlite-wal"))
                        try? FileManager.default.removeItem(at: defaultStoreURL.deletingLastPathComponent().appendingPathComponent("ckAssetFiles"))
                    })
                } catch {
                    //TODO: Handle error
                }
            }

            // change URL from default to shared location
            container.persistentStoreDescriptions.first!.url = sharedStoreURL

            let description = container.persistentStoreDescriptions.first!
            description.cloudKitContainerOptions = NSPersistentCloudKitContainerOptions(containerIdentifier: "iCloud.com.yourdomain.yourapp")
        }
        
        container.loadPersistentStores { description, error in
            //TODO: Handle error
        }
        container.viewContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
        container.viewContext.automaticallyMergesChangesFromParent = true
    }
}