Protocol to make fetching model objects from core data easier

CoreDataGettable.swift

import Foundation
import CoreData

protocol CoreDataGettable where Self: NSManagedObject {
    static func getSingle(id: String, context: NSManagedObjectContext) -> Self?
    static func getList(accId: String, context: NSManagedObjectContext) -> [Self]
    static func getSingle(withPredicate predicate: String, args: CVarArg, context: NSManagedObjectContext) -> Self?
}

extension CoreDataGettable {
    static func getSingle(id: String, context: NSManagedObjectContext) -> Self? {
        let accId = "123"
        let request = Self.fetchRequest()
        request.predicate = NSPredicate(format: "id == %@ AND accID == %@", id, accId)

        let results = try? context.fetch(request)
        return results?.first as? Self
    }

    static func getList(accId: String, context: NSManagedObjectContext) -> [Self] {
        let request = Self.fetchRequest()
        request.predicate = NSPredicate(format: "accId == %@", accId)

        let results = try? context.fetch(request)

        return results?.compactMap { $0 as? Self } ?? []
    }

    static func getSingle(withPredicate predicate: String, args: CVarArg, context: NSManagedObjectContext) -> Self? {
        let request = Self.fetchRequest()
        request.predicate = NSPredicate(format: predicate, args)

        let results = try? context.fetch(request)
        return results?.first as? Self
    }
}

final class Contact: NSManagedObject { }
extension Contact: CoreDataGettable { }

extension Contact {
    static func getActiveContact() -> Contact? {
        let context = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
        return getSingle(withPredicate: "id == %@ AND isActive == %@", args: ["123", true], context: context)
    }
}

final class BlockedNumber: NSManagedObject { }
extension BlockedNumber: CoreDataGettable { }

let context = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)

let contact = Contact.getSingle(id: "1234", context: context) // contact has type Contact?
let contacts = Contact.getList(accId: "1234", context: context) // contacts has type [Contact]
let specificContact = Contact.getSingle(withPredicate: "id == %@ AND number == %@", args: ["123", "1234567890"], context: context)
let activeContact = Contact.getActiveContact()

let blockedNumber = BlockedNumber.getSingle(id: "1234", context: context) // blockedNumber has type BlockedNumber?
let blockedNumbers = BlockedNumber.getList(accId: "1234", context: context) // blockedNumbers has type [BlockedNumber]