Generic generator of an NSManagedObjectContext for interacting with a CoreData database

ContextGenerator.swift

import CoreData

/// Use `ContextGenerator.contextForDatabase(named:)` to generate an NSManagedObjectContext for interacting with CoreData
class ContextGenerator: NSObject {
    class func contextForDatabase(named databaseName: String, inMemoryOnly: Bool = false) -> NSManagedObjectContext? {
        return ContextGenerator.init(databaseName: databaseName, inMemoryOnly: inMemoryOnly)?.managedObjectContext
    }

    private let managedObjectContext: NSManagedObjectContext
    private let managedObjectModel: NSManagedObjectModel
    private let coordinator: NSPersistentStoreCoordinator

    private init?(databaseName: String, inMemoryOnly: Bool) {
        guard let modelURL = Bundle.main.url(forResource: databaseName, withExtension: "momd"),
            let model = NSManagedObjectModel(contentsOf: modelURL),
            let persistentCoordinator = ContextGenerator.coordinator(managedObjectModel: model, databaseName: databaseName) else {
                return nil
        }
        let tempCoordinator = ContextGenerator.inMemoryCoordinator(managedObjectModel: model) ?? persistentCoordinator
        let coordinator = inMemoryOnly
            ? tempCoordinator
            : persistentCoordinator

        let context = NSManagedObjectContext(concurrencyType: NSManagedObjectContextConcurrencyType.mainQueueConcurrencyType)
        context.persistentStoreCoordinator = coordinator

        self.managedObjectModel = model
        self.coordinator = coordinator
        self.managedObjectContext = context

        super.init()
    }

    private static func coordinator(managedObjectModel: NSManagedObjectModel, databaseName: String) -> NSPersistentStoreCoordinator? {
        guard let applicationDocumentsDirectory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).last else {
            return nil
        }
        let coordinator = NSPersistentStoreCoordinator(managedObjectModel: managedObjectModel)
        let url = applicationDocumentsDirectory.appendingPathComponent(databaseName + ".sqlite")

        do {
            let options = [
                NSMigratePersistentStoresAutomaticallyOption: true,
                NSInferMappingModelAutomaticallyOption: true
            ]
            try coordinator.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: url, options: options)
        } catch {
            print("Error creating persisitant store")
            abort()
        }

        if FileManager.default.fileExists(atPath: url.path) {
            do {
                try FileManager.default.setAttributes([FileAttributeKey.protectionKey: FileProtectionType.complete], ofItemAtPath: url.path)
            } catch {
                print("cannot set NSFileProtectionComplete attribute")
            }
        }
        return coordinator
    }

    private static func inMemoryCoordinator(managedObjectModel: NSManagedObjectModel) -> NSPersistentStoreCoordinator? {
        let persistentStoreCoordinator = NSPersistentStoreCoordinator(managedObjectModel: managedObjectModel)

        do {
            try persistentStoreCoordinator.addPersistentStore(ofType: NSInMemoryStoreType, configurationName: nil, at: nil, options: nil)
        } catch {
            print("Error creating persisitant store")
            abort()
        }
        return persistentStoreCoordinator
    }
}

Try NSPersistentContainer