在哪里放置 persistentStoreDescriptions ？在 Swift3 Coredata 样板堆栈

Question

我将我的 Coredata 迁移到了新版本，并放置了 persistentStoreDescriptions 在 loadPersistentStores 和应用程序不会崩溃但不会持久化数据之前，考虑到它在迁移之前运行良好，这是我的代码：

lazy var persistentContainer: NSPersistentContainer = {
    /*
     The persistent container for the application. This implementation
     creates and returns a container, having loaded the store for the
     application to it. This property is optional since there are legitimate
     error conditions that could cause the creation of the store to fail.
    */

    let container = NSPersistentContainer(name: "CoreTest3")

    let description = NSPersistentStoreDescription()

    description.shouldInferMappingModelAutomatically = true
    description.shouldMigrateStoreAutomatically = true

    container.persistentStoreDescriptions = [description]


    container.loadPersistentStores(completionHandler: { (storeDescription, error) in
        if let error = error as NSError? {
            // 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.

            /*
             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.
             */
            fatalError("Unresolved error \(error), \(error.userInfo)")
        }
    })


    return container
}()

Answer 1

根据文档，您必须在初始化持久存储描述时指定托管对象模型的 URL：

let description = NSPersistentStoreDescription(url: storeURL)

要获取 URL，请查看Bundle.URL(forResource:withExtension)