核心数据并发调试

Question

这是我的 CoreDataStack 文件。当我通过并发调试运行项目时，我的应用程序在添加 pin 后立即崩溃。我认为这是因为我尝试在与创建上下文的线程不同的线程中访问数据。为了解决这个问题，我需要所有数据访问都发生在与创建上下文的线程相同的线程中。我做错了什么？

Run project with -com.apple.CoreData.ConcurrencyDebug 1

import CoreData

struct CoreDataStack {

    // MARK: - Properties

    private let model: NSManagedObjectModel
    internal let coordinator: NSPersistentStoreCoordinator
    private let modelURL: URL
    internal let dbURL: URL
    internal let persistingContext: NSManagedObjectContext
    internal let backgroundContext: NSManagedObjectContext
    let context: NSManagedObjectContext

    // MARK: - Initializers

    init?(modelName: String) {

        // Assumes the model is in the main bundle
        guard let modelURL = Bundle.main.url(forResource: modelName, withExtension: "momd") else {
            print("Unable to find \(modelName)in the main bundle")
            return nil
        }
        self.modelURL = modelURL

        // Try to create the model from the URL
        guard let model = NSManagedObjectModel(contentsOf: modelURL) else {
            print("unable to create a model from \(modelURL)")
            return nil
        }
        self.model = model

        // Create the store coordinator
        coordinator = NSPersistentStoreCoordinator(managedObjectModel: model)

        // Create a persistingContext (private queue) and a child one (main queue)
        // create a context and add connect it to the coordinator
        persistingContext = NSManagedObjectContext(concurrencyType: .privateQueueConcurrencyType)
        persistingContext.persistentStoreCoordinator = coordinator

        context = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
        context.parent = persistingContext

        // Create a background context child of main context
        backgroundContext = NSManagedObjectContext(concurrencyType: .privateQueueConcurrencyType)
        backgroundContext.parent = context

        // Add a SQLite store located in the documents folder
        let fm = FileManager.default

        guard let docUrl = fm.urls(for: .documentDirectory, in: .userDomainMask).first else {
            print("Unable to reach the documents folder")
            return nil
        }

        self.dbURL = docUrl.appendingPathComponent("model.sqlite")

        // Options for migration
        let options = [NSInferMappingModelAutomaticallyOption: true,NSMigratePersistentStoresAutomaticallyOption: true]

        do {
            try addStoreCoordinator(NSSQLiteStoreType, configuration: nil, storeURL: dbURL, options: options as [NSObject : AnyObject]?)
        } catch {
            print("unable to add store at \(dbURL)")
        }
    }

    // MARK: - Utils

    func addStoreCoordinator(_ storeType: String, configuration: String?, storeURL: URL, options : [NSObject:AnyObject]?) throws {
        try coordinator.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: dbURL, options: nil)
    }
}

// MARK: - CoreDataStack (Removing Data)

internal extension CoreDataStack  {

    func dropAllData() throws {
        // delete all the objects in the db. This won't delete the files, it will
        // just leave empty tables.
        try coordinator.destroyPersistentStore(at: dbURL, ofType: NSSQLiteStoreType , options: nil)
        try addStoreCoordinator(NSSQLiteStoreType, configuration: nil, storeURL: dbURL, options: nil)
    }
}

// MARK: - CoreDataStack (Batch Processing in the Background)

extension CoreDataStack {

    typealias Batch = (_ workerContext: NSManagedObjectContext) -> ()

    func performBackgroundBatchOperation(_ batch: @escaping Batch) {

        backgroundContext.perform() {

            batch(self.backgroundContext)

            // Save it to the parent context, so normal saving
            // can work
            do {
                try self.backgroundContext.save()
            } catch {
                fatalError("Error while saving backgroundContext: \(error)")
            }
        }
    }
}

// MARK: - CoreDataStack (Save Data)

extension CoreDataStack {

    func save() {
        context.performAndWait() {
            if self.context.hasChanges {
                do {
                    try self.context.save()
                } catch {
                    fatalError("Error while saving main context: \(error)")
                }
                self.persistingContext.perform() {
                    do {
                        try self.persistingContext.save()
                    } catch {
                        fatalError("Error while saving persisting context: \(error)")
                    }
                }
            }
        }
    }

    func autoSave(_ delayInSeconds : Int) {
        if delayInSeconds > 0 {
            do {
                try self.context.save()
                print("Autosaving")
            } catch {
                print("Error while autosaving")
            }
            let delayInNanoSeconds = UInt64(delayInSeconds) * NSEC_PER_SEC
            let time = DispatchTime.now() + Double(Int64(delayInNanoSeconds)) / Double(NSEC_PER_SEC)

            DispatchQueue.main.asyncAfter(deadline: time) {
                self.autoSave(delayInSeconds)
            }
        }
    }
}

Answer 1

确保在主线程中进行所有 UI 更改。