Persistence Controller Example

Check out this sample of the Persistence Controller with CloudKit generated by Xcode while creating a new project.

Francesco Leoni

2 min read

import CoreData

struct PersistenceController {

static let shared = PersistenceController()

static var preview: PersistenceController = {

let result = PersistenceController(inMemory: true)

let viewContext = result.container.viewContext

for _ in 0..<10 {

let newItem = Item(context: viewContext)

newItem.timestamp = Date()

}

do {

try viewContext.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)")

}

return result

}()

let container: NSPersistentCloudKitContainer

init(inMemory: Bool = false) {

container = NSPersistentCloudKitContainer(name: "Example")

if inMemory {

container.persistentStoreDescriptions.first!.url = URL(fileURLWithPath: "/dev/null")

}

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 functi 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)")

}

})

container.viewContext.automaticallyMergesChangesFromParent = true

}

}

If you have any question about this article, feel free to email me or tweet me @franceleonidev and share your opinion.

Thank you for reading and see you in the next article!

Share this article

Related articles


From REST API to CoreData in One Step

See how to convert fetched data from a REST API to entities and persist them to CoreData, the built-in local database of Apple.

3 min read

REST APICoreData

How To Use Markdown in SwiftUI

Discover different ways to use Markdown with the Text element in SwiftUI to easily add markdown text to your app.

1 min read

SwiftUI

Force Dark Mode to View in SwiftUI

In this article we are going to learn how to apply a specific colour scheme to a View regardless of the system dark mode.

1 min read

SwiftUI