CoreData Stack for both iOS 9 and iOS 10 in Swift

Question

I am trying to add Core Data to my existing project which supports iOS 9+.

I have added code generated by Xcode:

// MARK: - Core Data stack

    lazy var persistentContainer: NSPersistentContainer = {

        let container = NSPersistentContainer(name: "tempProjectForCoreData")
        container.loadPersistentStores(completionHandler: { (storeDescription, error) in
            if let error = error as NSError? {

                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 {
                let nserror = error as NSError
                fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
            }
        }
    }

After generating standard CoreData Stack in Xcode I found out that the new class of NSPersistentContainer is available from iOS 10 and as a result I get an error.

How should correct CoreData Stack should look like to support both iOS 9 and 10?

Answer 1

Here is the Core Data Stack that worked for me. I thought that in order to support iOS 10 I need to implement NSPersistentContainer class, but I found out that the older version with NSPersistentStoreCoordinator works as well.

You have to change name for your Model (coreDataTemplate) and project (SingleViewCoreData).

Swift 3:

// MARK: - CoreData Stack

    lazy var applicationDocumentsDirectory: URL = {
        // The directory the application uses to store the Core Data store file. This code uses a directory named "com.cadiridris.coreDataTemplate" in the application's documents Application Support directory.
        let urls = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
        return urls[urls.count-1]
    }()

    lazy var managedObjectModel: NSManagedObjectModel = {
        // The managed object model for the application. This property is not optional. It is a fatal error for the application not to be able to find and load its model.
        let modelURL = Bundle.main.url(forResource: "coreDataTemplate", withExtension: "momd")!
        return NSManagedObjectModel(contentsOf: modelURL)!
    }()

    lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator = {
        // The persistent store coordinator for the application. This implementation creates and returns a coordinator, having added 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.
        // Create the coordinator and store
        let coordinator = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
        let url = self.applicationDocumentsDirectory.appendingPathComponent("SingleViewCoreData.sqlite")
        var failureReason = "There was an error creating or loading the application's saved data."
        do {
            try coordinator.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: url, options: nil)
        } catch {
            // Report any error we got.
            var dict = [String: AnyObject]()
            dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data" as AnyObject?
            dict[NSLocalizedFailureReasonErrorKey] = failureReason as AnyObject?

            dict[NSUnderlyingErrorKey] = error as NSError
            let wrappedError = NSError(domain: "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict)
            // Replace this with code to handle the error appropriately.
            // abort() 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.
            NSLog("Unresolved error \(wrappedError), \(wrappedError.userInfo)")
            abort()
        }

        return coordinator
    }()

    lazy var managedObjectContext: NSManagedObjectContext = {
        // Returns the managed object context for the application (which is already bound to the persistent store coordinator for the application.) This property is optional since there are legitimate error conditions that could cause the creation of the context to fail.
        let coordinator = self.persistentStoreCoordinator
        var managedObjectContext = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
        managedObjectContext.persistentStoreCoordinator = coordinator
        managedObjectContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
        return managedObjectContext
    }()

    // MARK: - Core Data Saving support

    func saveContext () {
        if managedObjectContext.hasChanges {
            do {
                try managedObjectContext.save()
            } catch {
                // Replace this implementation with code to handle the error appropriately.
                // abort() 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
                NSLog("Unresolved error \(nserror), \(nserror.userInfo)")
                abort()
            }
        }
    }

Answer 2

Use the next Struct for ios 9 and 10

this is for context use the nex and replace ModelCoreData for your Model name of CoreData Storage.share.context

import Foundation import CoreData

/// NSPersistentStoreCoordinator extension extension NSPersistentStoreCoordinator {

/// NSPersistentStoreCoordinator error types
public enum CoordinatorError: Error {
    /// .momd file not found
    case modelFileNotFound
    /// NSManagedObjectModel creation fail
    case modelCreationError
    /// Gettings document directory fail
    case storePathNotFound
}

/// Return NSPersistentStoreCoordinator object
static func coordinator(name: String) throws -> NSPersistentStoreCoordinator? {

    guard let modelURL = Bundle.main.url(forResource: name, withExtension: "momd") else {
        throw CoordinatorError.modelFileNotFound
    }

    guard let model = NSManagedObjectModel(contentsOf: modelURL) else {
        throw CoordinatorError.modelCreationError
    }

    let coordinator = NSPersistentStoreCoordinator(managedObjectModel: model)

    guard let documents = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).last else {
        throw CoordinatorError.storePathNotFound
    }

    do {
        let url = documents.appendingPathComponent("\(name).sqlite")
        let options = [ NSMigratePersistentStoresAutomaticallyOption : true,
                        NSInferMappingModelAutomaticallyOption : true ]
        try coordinator.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: url, options: options)
    } catch {
        throw error
    }

    return coordinator
}

}

struct Storage {

static var shared = Storage()

@available(iOS 10.0, *)
private lazy var persistentContainer: NSPersistentContainer = {
    let container = NSPersistentContainer(name: "ModelCoreData")
    container.loadPersistentStores { (storeDescription, error) in
        print("CoreData: Inited \(storeDescription)")
        guard error == nil else {
            print("CoreData: Unresolved error \(String(describing: error))")
            return
        }
    }
    return container
}()

private lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator? = {
    do {
        return try NSPersistentStoreCoordinator.coordinator(name: "ModelCoreData")
    } catch {
        print("CoreData: Unresolved error \(error)")
    }
    return nil
}()

private lazy var managedObjectContext: NSManagedObjectContext = {
    let coordinator = self.persistentStoreCoordinator
    var managedObjectContext = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
    managedObjectContext.persistentStoreCoordinator = coordinator
    return managedObjectContext
}()

// MARK: Public methods

enum SaveStatus {
    case saved, rolledBack, hasNoChanges
}

var context: NSManagedObjectContext {
    mutating get {
        if #available(iOS 10.0, *) {
            return persistentContainer.viewContext
        } else {
            return managedObjectContext
        }
    }
}

mutating func save() -> SaveStatus {
    if context.hasChanges {
        do {
            try context.save()
            return .saved
        } catch {
            context.rollback()
            return .rolledBack
        }
    }
    return .hasNoChanges
}
func deleteAllData(entity: String)
{
    // let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
    let managedContext = Storage.shared.context
    let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: entity)
    fetchRequest.returnsObjectsAsFaults = false

    do
    {
        let results = try managedContext.fetch(fetchRequest)
        for managedObject in results
        {
            let managedObjectData:NSManagedObject = managedObject as! NSManagedObject
            managedContext.delete(managedObjectData)
        }
    } catch let error as NSError {
        print("Detele all data in \(entity) error : \(error) \(error.userInfo)")
    }
}

}