How to solve coreData error in AppDelegate? - ios

Question

Actually I have some experience in coreData with iOS 10.
But I now create an app thats tartget is #version 8.0 and above.
First I create an app including coreData. So they auto generate me a code in AppDelegate as iOS 10 standard. When I change the target 10 to 8.0 the AppDelegate shows some errors.
Error in AppDelegate
How to solve this? I want to use coreData in ios 8.0 and above.
// MARK: - Core Data stack
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: "coreDataTestForPreOS")
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
}()
// 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("Unresolved error \(nserror), \(nserror.userInfo)")
}
}
}
}
let ad = UIApplication.shared.delegate as! AppDelegate
let context = ad.persistentContainer.viewContext

Answer 1

var context: NSManagedObjectContext?
if #available(iOS 10.0, *) {
context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
} else {
// iOS 9.0 and below - however you were previously handling it
guard let modelURL = Bundle.main.url(forResource: "Model", withExtension:"momd") else {
fatalError("Error loading model from bundle")
}
guard let mom = NSManagedObjectModel(contentsOf: modelURL) else {
fatalError("Error initializing mom from: \(modelURL)")
}
let psc = NSPersistentStoreCoordinator(managedObjectModel: mom)
context = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
let urls = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
let docURL = urls[urls.endIndex-1]
let storeURL = docURL.appendingPathComponent("Model.sqlite")
do {
try psc.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: storeURL, options: nil)
} catch {
fatalError("Error migrating store: \(error)")
}
}`

Answer 2

Before the convenience of NSPersistentContainer there was NSPersistentStoreCoordinator. You'll need to create one of those:
if
let modelURL = Bundle.main.url(forResource: "Model", withExtension: "momd"),
let model = NSManagedObjectModel(contentsOf: modelURL),
let psc = NSPersistentStoreCoordinator(managedObjectModel: model) {
...
}
and then create and add one or more NSPersistentStores to it via .addPersistentStore(ofType:configurationName:at:options).