ViewModelFetchedResults.swift

extension ContentView {
    final class ViewModel: NSObject, NSFetchedResultsControllerDelegate, ObservableObject {
        private let colorController: NSFetchedResultsController<ColorItem>
        
        init(managedObjectContext: NSManagedObjectContext) {
            let sortDescriptors = [NSSortDescriptor(keyPath: \ColorItem.hex, ascending: true)]
            colorController = ColorItem.resultsController(context: managedObjectContext, sortDescriptors: sortDescriptors)
            super.init()
            colorController.delegate = self
            try? colorController.performFetch()
        }
        
        func controllerWillChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
            objectWillChange.send()
        }
        
        var colors: [ColorItem] {
            return colorController.fetchedObjects ?? []
        }
    }
}

extension ColorItem {
    static func resultsController(context: NSManagedObjectContext, sortDescriptors: [NSSortDescriptor] = []) -> NSFetchedResultsController<ColorItem> {
        let request = NSFetchRequest<ColorItem>(entityName: "ColorItem")
        request.sortDescriptors = sortDescriptors.isEmpty ? nil : sortDescriptors
        return NSFetchedResultsController(fetchRequest: request, managedObjectContext: context, sectionNameKeyPath: nil, cacheName: nil)
    }
}