向CoreData添加新版本

设置持久存储协调器时,请确保指定希望它在设置时传递的选项字典中自动迁移数据(如果适用)。

像这样:

    do {
        try self?.psc?.addPersistentStore(
                       ofType: NSSQLiteStoreType, 
            configurationName: nil, 
                           at: url, 
                      options: [
                             NSMigratePersistentStoresAutomaticallyOption: true,
                             NSInferMappingModelAutomaticallyOption: true
                        ])
        print("Core Data Store setup")
    } catch {
        print("Error migrating store: \(error)")
    }

如果您正在为iOS 10+构建,另一个选择是使用NSPersistentContainer,它为您管理上下文、模型和持久存储协调器。

(我还没有尝试过使用nspersistentcontainer进行迁移,但我想我会让您了解它们,以防它简化了您的工作)。

下面是一个使用nsPersistentContainer的核心数据堆栈示例,而不是使用带有持久存储协调器的旧样式,等等:

import CoreData

class CoreDataStack {

    // added in case you want to initialize the persistent container with a specific managed
    // object model via
    // let container = NSPersistentContainer.init(name: DataModel, managedObjectModel: managedObjectModel())
    internal func managedObjectModel() -> NSManagedObjectModel {
        let bundle = Bundle(for: AppDelegate.self)
        guard let url = bundle.url(forResource: "DataModel", withExtension: "momd") else {
            fatalError("Error loading model from bundle")
        }
        guard let mom = NSManagedObjectModel(contentsOf: url) else {
            fatalError("Error initializing mom from: \(url)")
        }

        return mom
    }

    internal lazy var persistentContainer: NSPersistentContainer = {
        let container = NSPersistentContainer(name: "DataModel")
        container.loadPersistentStores(completionHandler: { [weak self](storeDescription, error) in

            /*
             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.
             */
            if let error = error {
                print("CoreData:  error \(error), \(String(describing: error._userInfo))")
            }
        })
        return container
    }()

    func performUITask(_ block: @escaping (NSManagedObjectContext) -> Void) {
        persistentContainer.viewContext.perform {
            block(self.persistentContainer.viewContext)
        }
    }

    func performBackgroundTask(_ block: @escaping (NSManagedObjectContext) -> Void) {
        persistentContainer.performBackgroundTask(block)
    }

    // MARK: - Core Data Saving support
    func saveContext () {
        let context = persistentContainer.viewContext
        if context.hasChanges {
            do {
                try context.save()
            } catch {
                // Replace this implementation with code to handle the error appropriately.
                // fatalError() 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.
                let nserror = error as NSError
                fatalError("CoreData: Unresolved error \(nserror), \(nserror.userInfo)")
            }
        }
    }
}