ios – Why I get Multithreading_Violation_AllThatIsLeftToUsIsHonor for this easiest NSAsynchronousFetchRequest use case?

I need to begin studying to make use of NSAsynchronousFetchRequest by referring to https://www.marcosantadev.com/coredata_crud_concurrency_swift_2/

I’ve the only use case of NSAsynchronousFetchRequest

NSAsynchronousFetchRequest

// Name from UI primary thread
func X() {
    let fetchRequest = NSFetchRequest<NSPlainNote>(entityName: "NSPlainNote")
    
    let asynchronousFetchRequest = NSAsynchronousFetchRequest(fetchRequest: fetchRequest) { asynchronousFetchResult in
        guard let end result = asynchronousFetchResult.finalResult as? [NSPlainNote] else { return }
    }

    let coreDataStack = CoreDataStack.INSTANCE
    // backgroundContext created through persistentContainer.newBackgroundContext()
    let backgroundContext = coreDataStack.backgroundContext
    
    backgroundContext.carry out {
        do {
            attempt backgroundContext.execute(asynchronousFetchRequest)
        } catch let error {
            backgroundContext.rollback()
            
            error_log(error)
        }
    }
}

Nonetheless, operating the above code will get me the next error

CoreData`+[NSManagedObjectContext
Multithreading_Violation_AllThatIsLeftToUsIsHonor]:

If I modify the code by utilizing NSFetchRequest immediately.

NSFetchRequest

// Name from UI primary thread
func X() {
    let fetchRequest = NSFetchRequest<NSPlainNote>(entityName: "NSPlainNote")

    let coreDataStack = CoreDataStack.INSTANCE
    // backgroundContext created through persistentContainer.newBackgroundContext()
    let backgroundContext = coreDataStack.backgroundContext
    
    backgroundContext.carry out {
        do {
            let nsPlainNotes = attempt fetchRequest.execute()
        } catch let error {
            backgroundContext.rollback()
            
            error_log(error)
        }
    }
}

Factor works high quality. Might I do know, what’s improper with my NSAsynchronousFetchRequest model of code?

That is my CoreDataStack.swift for reference objective.

CoreDataStack.swift

import CoreData

class CoreDataStack {
    static let INSTANCE = CoreDataStack()
    
    non-public init() {
    }
    
    non-public(set) lazy var persistentContainer: NSPersistentContainer = {
        let container = NSPersistentContainer(title: "wenote")
        
        container.loadPersistentStores(completionHandler: { (storeDescription, error) in
            if let error = error as NSError? {
                // It is a severe deadly error. We'll simply merely terminate the app, slightly than utilizing error_log.
                fatalError("Unresolved error (error), (error.userInfo)")
            }
        })
        
        // In order that when backgroundContext write to persistent retailer, container.viewContext will retrieve replace from
        // persistent retailer.
        container.viewContext.automaticallyMergesChangesFromParent = true
        
        // TODO: Undecided these are required...
        //
        //container.viewContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
        //container.viewContext.undoManager = nil
        //container.viewContext.shouldDeleteInaccessibleFaults = true
        
        return container
    }()
    
    non-public(set) lazy var backgroundContext: NSManagedObjectContext = {
        let backgroundContext = persistentContainer.newBackgroundContext()

        // Comparable conduct as Android's Room OnConflictStrategy.REPLACE
        backgroundContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
        
        // TODO: Undecided these are required...
        //backgroundContext.undoManager = nil
        
        return backgroundContext
    }()
}