Question

我尝试使用swift 3获取结果控制器，但它不起作用。我看到，我的实体已经使用我自己的获取请求添加到Core Data，但是frc没有看到它们。如果我重新启动我的应用程序，新元素将出现在表格中。

创建FRC：

func getFRCForChats() -> NSFetchedResultsController<Conversation>{
    var fetchedResultsController: NSFetchedResultsController<Conversation>

    let fetchRequest: NSFetchRequest<Conversation> = Conversation.fetchRequest()
    let sortDescriptor = NSSortDescriptor(key: "conversationID", ascending: true)

    fetchRequest.sortDescriptors = [sortDescriptor]

    fetchedResultsController = NSFetchedResultsController<Conversation>(fetchRequest:
        fetchRequest, managedObjectContext: container.viewContext, sectionNameKeyPath: nil, cacheName: nil)

    return fetchedResultsController
}

使用FRC：

   var fetchedResultsController: NSFetchedResultsController<Conversation>!

override func viewDidLoad() {
    super.viewDidLoad()

    tableView.delegate = self
    tableView.dataSource = self

    coreDataService = CoreDataService()
    fetchedResultsController = coreDataService.getFRCForChats()
    fetchedResultsController.delegate = self
    try! fetchedResultsController.performFetch()
}

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    if(!fetchedResultsController.sections!.isEmpty) {
        if let sectionInfo = fetchedResultsController.sections?[section]{
            return sectionInfo.numberOfObjects
        } else { print("Unexpected Section") }
    }
    return 0
}

func numberOfSections(in tableView: UITableView) -> Int {
    if let count = fetchedResultsController.sections?.count {
        return count
    } else {
        return 0
    }
}


func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "ChatCell", for: indexPath) as!ChatTableViewCell

    //cell.name.text = cells[indexPath.row]

    let conversation = fetchedResultsController.object(at: indexPath)

    if let participants = conversation.participants as? Set<User> {

        conversation.managedObjectContext?.performAndWait {
            for user in participants{
                cell.name.text = user.name
                break
            }
        }
    }


    return cell

}

添加新实体：

var k = 2
@IBAction func createConversation(_ sender: Any) {
    coreDataService.insertConversation(id: k)
    k += 1
}



 func insertConversation(id: Int) {

    container.performBackgroundTask { (context) in


    let user = User.findOrInsertUser(id: id, name: "Andrew", mobilePhone: 234567, avatar: nil, inContext: context)

    _ = Conversation.findOrInsertConversation(id: id + 100, summa: Double(12+id), users: [user], transactions: [], inContext: context)

        context.saveThrows()
    }

    let request: NSFetchRequest<Conversation> = Conversation.fetchRequest()

    container.viewContext.perform {
        if let results = try? self.container.viewContext.fetch(request) {
            print("\(results.count) TweetMs")
            for result in results{
                print(result.conversationID, result.summa)
            }
        }
    }
}

代表：

extension ChatsViewController: NSFetchedResultsControllerDelegate {
func controllerWillChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
    tableView.beginUpdates()
}

func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
    tableView.endUpdates()
}

func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {
    switch type {
    case .delete:
        if let indexPath = indexPath {
            tableView.deleteRows(at: [indexPath], with: .automatic)
        }
    case .insert:
        if let newIndexPath = newIndexPath {
            tableView.insertRows(at: [newIndexPath], with: .automatic)
        }
    case .move:
        if let indexPath = indexPath {
            tableView.deleteRows(at: [indexPath], with: .automatic)
        }

        if let newIndexPath = newIndexPath {
            tableView.insertRows(at: [newIndexPath], with: .automatic)
        }
    case .update:
        if let indexPath = indexPath {
            tableView.reloadRows(at: [indexPath], with: .automatic)
        }
    }
}

func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange sectionInfo: NSFetchedResultsSectionInfo, atSectionIndex sectionIndex: Int, for type: NSFetchedResultsChangeType) {
    switch type {
    case .delete:
        tableView.deleteSections(IndexSet(integer: sectionIndex),
                                 with: .automatic)
    case .insert:
        tableView.insertSections(IndexSet(integer: sectionIndex),
                                 with: .automatic)
    case .move, .update: break
    }
}
}

编辑：如果我在每次编辑上下文后调用performFetch（），表重新加载而不调用委托。

Answer 1

正如Apple Docs所述：

automaticallyMergesChangesFromParent

一个布尔值，指示上下文是否自动合并   更改保存到其持久性存储协调器或父上下文。

尝试将其设置为true

container.viewContext.automaticallyMergesChangesFromParent = true

至少为我解决了类似的问题。

获取结果控制器不会在运行时更新表

1 个答案: