Swift 2 to Swift 3 Core Data in Xcode 9 - How can I port over existing Core Data "data" already saved? - ios

Question

I have an older project/app that I want to bring up to a 3.x version of Swift from Swift 2. In the course of porting the code over I recreated a new project with the same bundle id to start fresh and imported the code over.
Everything is working now in Swift 3.2 in Xcode 9 except for Core Data. Any device running an older version of the app crashes when accessing Core Data.
THe specific error is in the loading of the NSManagedObjectModel.
OLD SWIFT 2 WAY:
My CoreData File is called: "MyApp.xcdatamodeld"
lazy var managedObjectModel: NSManagedObjectModel = {
let modelURL = NSBundle.mainBundle().URLForResource("MyApp", withExtension: "momd")!
return NSManagedObjectModel(contentsOfURL: modelURL)!
}()
NEW SWIFT 3 WAY:
My new CoreData File is called: "MyApp.xcdatamodel"
lazy var managedObjectModel: NSManagedObjectModel = {
if let modelURL = Bundle.main.url(forResource: "MyApp", withExtension: "xcdatamodel") {
return NSManagedObjectModel(contentsOf: modelURL)!
} else {
let modelURLOld = Bundle.main.url(forResource: "MyApp", withExtension: "momd")
return NSManagedObjectModel(contentsOf: modelURLOld!)!
}
}
When I run the code I get the following errors:
CoreData: annotation: Failed to load optimized model at path '/var/containers/Bundle/Application/50367482-FC2C-4553-B04B-68AD922B8128/MyApp.app/MyApp.momd/MyApp.omo'
Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'NSFetchRequest could not locate an NSEntityDescription for entity name 'UMyAppModel''
So my new app code is not finding the the files to load for CoreData.
How can I can load these older CoreData files into my app? If need be I can set up a migration but the issue is that I can't see the older Core data files.
One way I can get the app to run is to add the following code:
let objectModel = NSManagedObjectModel.mergedModel(from: [Bundle.main])
return objectModel!
However none of the previous historical data is loaded into the app.
How can I migrate or get access to the original Coredata data to migrate into the new Coredata files on devices that have the old code version (swift 2) of the app?

Answer 1

Fixed the issue. It was related to the way the NSPersistentContainer was being initialized in my app. The swift 3 boiler plate code was not migrating to the new data store nor looking for the old sqlite db (which I suspect was ultimately the main cause of the data not being found).
My code:
lazy var persistentContainer: NSPersistentContainer = {
let modelURL = Bundle.main.url(forResource: "MyApp", withExtension: "momd")!
let container = NSPersistentContainer(name: "MyApp", managedObjectModel: NSManagedObjectModel(contentsOf: modelURL)!)
let documentsDirectory = FileManager.default.urls(for: FileManager.SearchPathDirectory.documentDirectory, in: FileManager.SearchPathDomainMask.userDomainMask)
let storeUrl = self.applicationDocumentsDirectory.appendingPathComponent("MyApp.sqlite")
let description = NSPersistentStoreDescription()
description.shouldInferMappingModelAutomatically = true
description.shouldMigrateStoreAutomatically = true
container.persistentStoreDescriptions = [description]
container.persistentStoreDescriptions = [NSPersistentStoreDescription(url: storeUrl)]
container.loadPersistentStores(completionHandler: { (storeDescription, error) in
if let error = error as NSError? {
fatalError("Unresolved error \(error), \(error.userInfo)")
}
})
return container
}()