swift - 添加新联系人后未调用controllerDidChangeContent

Question

基本上看起来我的 NSFetchedResultsController 没有检测到更改，所以我什至不认为在这里创建的新对象正在被保存。

else if segue.identifier == "AddContact" {
        let navigationController = segue.destinationViewController as! UINavigationController
        let addViewController = navigationController.topViewController as! NewContactViewController
        let contactEntity = NSEntityDescription.entityForName("Contact", inManagedObjectContext: context)
        let newContact = Contact(entity: contactEntity!, insertIntoManagedObjectContext: context)

        addViewController.contact = newContact
        addViewController.context = newContact.managedObjectContext
        addViewController.delegate = self
    }

用户按“完成”返回到联系人 ListView 后，将根据我创建的委托(delegate)调用此函数。

func didFinishViewController(viewController:NewContactViewController, didSave:Bool) {

    // 1
    if didSave {
        // 2
        let context = viewController.context
        context.performBlock({ () -> Void in
            if context.hasChanges {
                do {
                    try context.save()
                } catch {
                    let nserror = error as NSError
                    print("Error: \(nserror.localizedDescription)")
                    abort()
                }
            }

            // 3
            self.coreDataStack.saveContext()
        })
    }

在检查上下文数百万次后，它们始终匹配，因此推送工作正常，但似乎正在记录更改。 CoreDataStack.swift 就是这样。

//exablishes the directory to be used for the stack in SQLite fashion
private lazy var applicationDocumentsDirectory: NSURL = {
    let urls = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)
    return urls[urls.count-1]
}()

//establishes the object model that interacts with the GUI object data model
private lazy var managedObjectModel: NSManagedObjectModel = {
    let modelURL = NSBundle.mainBundle().URLForResource(self.modelName, withExtension: "momd")!
    return NSManagedObjectModel(contentsOfURL: modelURL)!
}()

//establishes the coordinator that connects the managed context with the persistent store
private lazy var psc: NSPersistentStoreCoordinator = { let coordinator = NSPersistentStoreCoordinator(
    managedObjectModel: self.managedObjectModel)

    let url = self.applicationDocumentsDirectory.URLByAppendingPathComponent(self.modelName + ".sqlite")

    do {
        let options = [NSMigratePersistentStoresAutomaticallyOption : true]

        try coordinator.addPersistentStoreWithType( NSSQLiteStoreType, configuration: nil, URL: url, options: nil) //establishes the actual persistent store
    } catch {
        print("Error adding persistent store.")
    }
    return coordinator
}()


//establishes the managed context by which managed objects interact in reading and writing
lazy var context: NSManagedObjectContext = {
    var managedObjectContext = NSManagedObjectContext(concurrencyType: .MainQueueConcurrencyType)
    managedObjectContext.persistentStoreCoordinator = self.psc
    return managedObjectContext
}()

func saveContext () {
    if context.hasChanges {
        do {
            try context.save()
        } catch {
            let nserror = error as NSError
            print("Error: \(nserror.localizedDescription)")
            abort()
        }
    }
}

NSFetchedResultsController 实现

// MARK: Fetched Results controller
func contactListFetchedResultsController()-> NSFetchedResultsController {

    fetchedResultController = NSFetchedResultsController(fetchRequest: contactListFetchRequest(), managedObjectContext: coreDataStack.context, sectionNameKeyPath: nil, cacheName: nil)
    fetchedResultController.delegate = self

    do {
        try fetchedResultController.performFetch()
    } catch let error as NSError {
        print("Error: \(error.localizedDescription)")
        abort()
    }

        return fetchedResultController
}

func contactListFetchRequest() -> NSFetchRequest {

    let fetchRequest = NSFetchRequest(entityName: "Contact")
    fetchRequest.fetchBatchSize = 20

    let sortDescriptor = NSSortDescriptor(key: "firstName", ascending: true)

    fetchRequest.sortDescriptors = [sortDescriptor]

    return fetchRequest
}

Answer 1

当你已经在 UI 线程上时，为什么还要有 context.performBlock ？您正在处理不止一种环境吗？

假设您使用多个上下文，您将在子上下文之前将主上下文保存为 performBlock()，同时使子上下文在之后保存调用 self.coreDataStack.saveContext()。

由于这是所有与 UI 相关的代码，因此您最好只使用整个 UI 的主队列上下文，并且我怀疑您的 NSFetchedResultsController 将开始接收通知。