Setting up a Core Data stack manually

Overview

If your app targets iOS 10+, macOS 10.12+, tvOS 10+, watchOS 3+, or visionOS 1+, you can use NSPersistentContainer to simplify creation and management of the Core Data stack. Otherwise, you need to manually create an NSManagedObjectModel, NSPersistentStoreCoordinator, and at least one NSManagedObjectContext.

Create a managed object model

To instantiate an NSManagedObjectModel, pass in a URL that points to the compiled version of the .xcdatamodeld file. This .momd file is typically part of your app bundle.

// Get a URL to the compiled model in the app bundle.
guard let modelURL = Bundle.main.url(forResource: "DataModel",
                                     withExtension: "momd") else {
    fatalError("Failed to find data model")
}

// Use the URL to create a managed object model.
guard let model = NSManagedObjectModel(contentsOf: modelURL) else {
    fatalError("Failed to create model from file: \(modelURL)")
}

Create a persistent store coordinator

Next, pass the managed object model to the NSPersistentStoreCoordinator initializer to create a store coordinator with that model.

// Use the managed object model to create a persistent store coordinator.
let coordinator = NSPersistentStoreCoordinator(managedObjectModel: managedObjectModel)

Add a persistent store to the coordinator

If you want Core Data to persist your data model to disk, tell the store coordinator where the file exists and what format to use.

// Get the URL to the Document directory.
let documentDirectoryURL = FileManager.default.urls(for: .documentDirectory,
                                                    in: .userDomainMask).last
// Create a URL to the data store.
guard let storeURL = URL(string: "DataModel.sqlite",
                         relativeTo: documentDirectoryURL) else {
    fatalError("Failed to create store URL")
}

do {
    // Set the options to enable lightweight data migrations.
    let options = [NSMigratePersistentStoresAutomaticallyOption: true,
                         NSInferMappingModelAutomaticallyOption: true]
    // Add the store to the coordinator.
    _ = try coordinator.addPersistentStore(type: .sqlite, at: storeURL,
                                       options: options)
} catch {
    fatalError("Failed to add persistent store: \(error.localizedDescription)")
}

There are advantages and disadvantages to each of the store types. Refer to the NSPersistentStoreCoordinator documentation for details on each store type.

Create a managed object context

Create an NSManagedObjectContext, and set its store coordinator property.

// Create a context to interact with managed objects.
let context = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
// Assign the coordinator to the context.
context.persistentStoreCoordinator = persistentStoreCoordinator

Your app uses this context to interact with Core Data. Pass a reference to this context to your user interface. For additional information, see Inject the managed object context.