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!

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