CoreDataStack.swift

import CoreData

protocol CoreDataServiceProtocol:class {
    var errorHandler: (Error) -> Void {get set}
    var persistentContainer: NSPersistentContainer {get}
    var managedObjectContext: NSManagedObjectContext {get}
    var backgroundContext: NSManagedObjectContext {get}
    func performBackgroundTask(_ block: @escaping (NSManagedObjectContext) -> Void)
    func performForegroundTask(_ block: @escaping (NSManagedObjectContext) -> Void)
}

final class CoreDataStack: CoreDataServiceProtocol {




    static let shared = CoreDataStack()
    var errorHandler: (Error) -> Void = {_ in }

    lazy var persistentContainer: NSPersistentContainer = {
        let container = NSPersistentContainer(name: "coredatainextension")

        container.loadPersistentStores(completionHandler: { (storeDescription, error) in
            if let error = error as NSError? {
            fatalError("Unresolved error (error), (error.userInfo)")
            }
        })



        return container
    }()

    lazy var managedObjectContext: NSManagedObjectContext = {
        return self.persistentContainer.viewContext
    }()

    lazy var backgroundContext: NSManagedObjectContext = {
        return self.persistentContainer.newBackgroundContext()
    }()

    func performForegroundTask(_ block: @escaping (NSManagedObjectContext) -> Void) {
        self.managedObjectContext.perform {
            block(self.managedObjectContext)
        }
    }

    func performBackgroundTask(_ block: @escaping (NSManagedObjectContext) -> Void) {
        self.persistentContainer.performBackgroundTask(block)
    }
}