What’s new in Core Data

5:39 - Adding a composite attribute

enum PaintColor: String, CaseIterable, Identifiable {
    case none, white, blue, orange, red, gray, green, gold, yellow, black
    var id: Self { self }
}

extension Aircraft {

    @nonobjc public class func fetchRequest() -> NSFetchRequest<Aircraft> {
        return NSFetchRequest<Aircraft>(entityName: "Aircraft")
    }

    @NSManaged public var aircraftCategory: String?
    @NSManaged public var aircraftClass: String?
    @NSManaged public var aircraftType: String?
    @NSManaged public var colorScheme: [String: Any]?
    @NSManaged public var photo: Data?
    @NSManaged public var tailNumber: String?
    @NSManaged public var logEntries: NSSet?

}

5:53 - Setting a composite attribute

private func addAircraft() {
    viewContext.performAndWait {
        let newAircraft = Aircraft(context: viewContext)
        
        newAircraft.tailNumber = tailNumber
        newAircraft.aircraftType = aircraftType
        newAircraft.aircraftClass = aircraftClass
        newAircraft.aircraftCategory = aircraftCategory
        
        newAircraft.colorScheme = [
            "primary": primaryColor.rawValue,
            "secondary": secondaryColor.rawValue,
            "tertiary": tertiaryColor.rawValue
        ]
        
        do {
            try viewContext.save()
        } catch {
            // ...
        }
    }
}

6:11 - Fetching a composite attribute

private func findAircraft(with color: String) {
    viewContext.performAndWait {
        let fetchRequest = Aircraft.fetchRequest()
        fetchRequest.predicate = NSPredicate(format: "colorScheme.primary == %@", color)
        
        do {
            var fetchedResults: [Aircraft]
            fetchedResults = try viewContext.fetch(fetchRequest)
            
            // ...
        } catch {
            // Handle any errors that may occur
        }
    }
}

16:00 - Creating managed object model references for staged migration

let v1ModelChecksum = "kk8XL4OkE7gYLFHTrH6W+EhTw8w14uq1klkVRPiuiAk="
let v1ModelReference = NSManagedObjectModelReference(
    modelName: "modelV1"
    in: NSBundle.mainBundle
    versionChecksum: v1ModelChecksum
)

let v2ModelChecksum = "PA0Gbxs46liWKg7/aZMCBtu9vVIF6MlskbhhjrCd7ms="
let v2ModelReference = NSManagedObjectModelReference(
    modelName: "modelV2"                          
    in: NSBundle.mainBundle                                                 
    versionChecksum: v2ModelChecksum
)

let v3ModelChecksum = "iWKg7bxs46g7liWkk8XL4OkE7gYL/FHTrH6WF23Jhhs="
let v3ModelReference = NSManagedObjectModelReference(
    modelName: "modelV3"
    in: NSBundle.mainBundle
    versionChecksum: v3ModelChecksum
)

16:19 - Creating migration stages for staged migration

let lightweightStage = NSLightweightMigrationStage([v1ModelChecksum])
lightweightStage.label = "V1 to V2: Add flightData attribute"

let customStage = NSCustomMigrationStage(
    migratingFrom: v2ModelReference,
    to: v3ModelReference
)

customStage.label = "V2 to V3: Denormalize model with FlightData entity"

16:54 - willMigrationHandler and didMigrationHandler of NSCustomMigrationStage

customStage.willMigrateHandler = { migrationManager, currentStage in
    guard let container = migrationManager.container else {
        return
    }

    let context = container.newBackgroundContext()
    try context.performAndWait {
        let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "Aircraft")
        fetchRequest.predicate = NSPredicate(format: "flightData != nil")
            
        do {
           var fetchedResults: [NSManagedObject]
           fetchedResults = try viewContext.fetch(fetchRequest)
           
           for airplane in fetchedResults {
                let fdEntity = NSEntityDescription.insertNewObject(
                    forEntityName: "FlightData,
                    into: context
                )
             
                let flightData = airplane.value(forKey: "flightData")
                fdEntity.setValue(flightData, forKey: “data”)
                fdEntity.setValue(airplane, forKey: "aircraft")
                airplane.setValue(nil, forKey: "flightData")
            }
            try context.save()
        } catch {
            // Handle any errors that may occur
        }
    }
}

17:41 - Loading the persistent stores with an NSStagedMigrationManager

let migrationStages = [lightweightStage, customStage]
let migrationManager = NSStagedMigrationManager(migrationStages)

let persistentContainer = NSPersistentContainer(
    path: "/path/to/store.sqlite",
    managedObjectModel: myModel
)

var storeDescription = persistentContainer?.persistentStoreDescriptions.first

storeDescription?.setOption(
    migrationManager,
    forKey: NSPersistentStoreStagedMigrationManagerOptionKey
)

persistentContainer?.loadPersistentStores { storeDescription, error in
    if let error = error {
        // Handle any errors that may occur
    }
}

21:01 - Adding a persistent store with NSPersistentStoreDeferredLightweightMigrationOptionKey option

let options = [
    NSPersistentStoreDeferredLightweightMigrationOptionKey: true,
    NSMigratePersistentStoresAutomaticallyOption: true,
    NSInferMappingModelAutomaticallyOption: true
]

let store = try coordinator.addPersistentStore(
    ofType: NSSQLiteStoreType,
    configurationName: nil,
    at: storeURL,
    options: options
)

21:17 - Executing deferred migrations

// After using BGProcessingTask to run migration work   
let metadata = coordinator.metadata(for: store)
if (metadata[NSPersistentStoreDeferredLightweightMigrationOptionKey] == true) {
    coordinator.finishDeferredLightweightMigration()
}