Question

我正在通过以下步骤进行核心数据的轻量级迁移：

版本化数据模型

创建新的与新数据模型兼容的persistenceStore。

lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator =   {
        // Initialize Persistent Store Coordinator
        let persistentStoreCoordinator = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)

        // URL Persistent Store
    let URLPersistentStore = self.applicationStoresDirectory().appendingPathComponent("FieldSense.sqlite")

        do {
            // Declare Options
            let options = [ NSMigratePersistentStoresAutomaticallyOption : true, NSInferMappingModelAutomaticallyOption : true ]

            // Add Persistent Store to Persistent Store Coordinator
            try persistentStoreCoordinator.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: URLPersistentStore, options: options)

        } catch {
            let fm = FileManager.default
            var isDir : ObjCBool = false
            if  fm.fileExists(atPath: (URLPersistentStore?.path)!, isDirectory: &isDir){
          //  if fm.fileExistsAtPath(URLPersistentStore.path!) {
                let nameIncompatibleStore = self.nameForIncompatibleStore()
                let URLCorruptPersistentStore = self.applicationIncompatibleStoresDirectory().appendingPathComponent(nameIncompatibleStore)

                do {
                    // Move Incompatible Store
                //    try fm.moveItemAtURL(URLPersistentStore, toURL: URLCorruptPersistentStore)
                    try fm.moveItem(at: URLPersistentStore!, to: URLCorruptPersistentStore!)

                } catch {
                    let moveError = error as NSError
                    print("\(moveError), \(moveError.userInfo)")
                }
            }

            do {
                // Declare Options
                let options = [ NSMigratePersistentStoresAutomaticallyOption : true, NSInferMappingModelAutomaticallyOption : true ]

                try persistentStoreCoordinator.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: URLPersistentStore, options: options)

            } catch {
                let storeError = error as NSError
                print("\(storeError), \(storeError.userInfo)")
            }

            // Update User Defaults
            let userDefaults = UserDefaults.standard
            userDefaults.set(true, forKey: "didDetectIncompatibleStore")
        }

        return persistentStoreCoordinator
}()

但是，当用户从应用商店更新应用时，现有的用户数据将被删除。可能是什么原因？

在核心数据迁移上保留现有数据

0 个答案: