带有预填充 .sqlite 的核心数据 (Swift3)

目前，我正在对现有 iOS9 应用程序进行 Swift3 / iOS10 更新，该应用程序存储了欧洲各地约 10,000 个电动汽车充电点。到目前为止，我总是为应用程序提供预填充的数据库（.xcappdata 包中的 .sqlite、.sqlite-shm、.sqlite-wal 文件），但在当前版本中，Apple 引入了NS持久化容器 https://developer.apple.com/reference/coredata/nspersistentcontainer类，这使得它变得更加复杂。在我的 AppDelegate 类中，我实例化 NSPercientContainer 对象并将其传递给惰性变量，就像 Apple 在每个示例代码中所做的那样：

   lazy var stationDataPersistentContainer: NSPersistentContainer = {  
     let fileMgr = FileManager.default
     let destinationModel = NSPersistentContainer.defaultDirectoryURL()
     if !fileMgr.fileExists(atPath: destinationModel.appendingPathComponent("StationData.sqlite").path) {
         do {
             try fileMgr.copyItem(at: URL(fileURLWithPath: Bundle.main.resourcePath!.appending("/StationData.sqlite")), to: destinationModel.appendingPathComponent("/StationData.sqlite"))
             try fileMgr.copyItem(at: URL(fileURLWithPath: Bundle.main.resourcePath!.appending("/StationData.sqlite-shm")), to: destinationModel.appendingPathComponent("/StationData.sqlite-shm"))
             try fileMgr.copyItem(at: URL(fileURLWithPath: Bundle.main.resourcePath!.appending("/StationData.sqlite-wal")), to: destinationModel.appendingPathComponent("/StationData.sqlite-wal"))
         } catch {
             //
         }
     } else {
         //
     }
     /* 
     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: "StationData")  
    container.loadPersistentStores(completionHandler: { (storeDescription, error) in  
         if let error = error as NSError? {  
             /* 
              * 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  
    }()

在 iOS 9 版本中，我将文件复制到适当的目录，如以下代码示例所示：

lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator = {  
    let coordinator = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)  
    let url = self.applicationDocumentsDirectory.URLByAppendingPathComponent("StationData.sqlite")  
    let fileMgr = NSFileManager.defaultManager()  
    if !fileMgr.fileExistsAtPath(url.path!) {  
         do {  
              try fileMgr.copyItemAtPath(NSBundle.mainBundle().pathForResource("StationData", ofType: "sqlite")!, toPath: self.applicationDocumentsDirectory.URLByAppment("StationData.sqlite").path!)  
              try fileMgr.copyItemAtPath(NSBundle.mainBundle().pathForResource("StationData", ofType: "sqlite-shm")!, toPath: self.applicationDocumentsDirectory.URLByAppendingPathComponent("StationData.sqlite-shm").path!)  
              try fileMgr.copyItemAtPath(NSBundle.mainBundle().pathForResource("StationData", ofType: "sqlite-wal")!, toPath: self.applicationDocumentsDirectory.URLByAppendingPathComponent("StationData.sqlite-wal").path!)  
         } catch {  
              //  
         } do {  
              try coordinator.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: url,  
                                                       options: [NSMigratePersistentStoresAutomaticallyOption:true, NSInferMappingModelAutomaticallyOption:true])  
         } catch {  
              //  
         }  
    } else {  
         //  
    }  
    return coordinator
}() 

几天来我一直尝试将文件移动到正确的目录，该目录由NSPersistentContainer.defaultDirectoryURL() -> URL，但每次我收到错误时，该文件已经存在，因为我的 stationDataPersistentContainer 已经初始化，因此 NSPersistentContainer 有足够的时间来生成 sqlite* 文件。即使我尝试复制文件并在覆盖的 init() 函数中初始化 stationDataPersistentContainer，我也无法做到这一点。文档中是否有我遗漏或忽略的内容？这是将应用程序安装时的现有数据复制到 coredata 的最佳/正确/适当的方法。

附录：

仅供参考，我还可以将从 API 获取的 JSON 文件存储到文档目录中并运行 JSON 解析器，但这需要大量资源，尤其是时间！（这个问题也发布在苹果开发者论坛上，等待批准）

我就是这样做的：

lazy var persistentContainer: NSPersistentContainer = {

         let container = NSPersistentContainer(name: "app_name")

        let seededData: String = "app_name"
        var persistentStoreDescriptions: NSPersistentStoreDescription

        let storeUrl = self.applicationDocumentsDirectory.appendingPathComponent("app_name.sqlite")

        if !FileManager.default.fileExists(atPath: (storeUrl.path)) {
            let seededDataUrl = Bundle.main.url(forResource: seededData, withExtension: "sqlite")
            try! FileManager.default.copyItem(at: seededDataUrl!, to: storeUrl)

        }

        print(storeUrl)


        container.persistentStoreDescriptions = [NSPersistentStoreDescription(url: storeUrl)]
        container.loadPersistentStores(completionHandler: { (storeDescription, error) in
            if let error = error {

                fatalError("Unresolved error \(error),")
            }
        })

         return container


    }()