NSFetchedResultsController未正确更新tableView

Question

我正在viewDidLoad中获取一些项(NSManagedObject(，并且我正在使用NSFetchedResultsController委托来更新swift ios中的tableView单元格(来自Apple文档的插入、删除等委托(，问题是当我将一个项添加到相同ManagedObject类型的核心数据中时，我希望表能用新项更新，但是，最后一项从表视图中删除，而不添加新项。我只在再次加载屏幕时看到新项目。。。可能出了什么问题？这是我的fetchedResultsController:

lazy var fetchedResultsController: NSFetchedResultsController<Message> = {
let context = CoreDataManager.shared.persistentContainer.viewContext
let request: NSFetchRequest<Message> = Message.fetchRequest()
request.sortDescriptors = [
NSSortDescriptor(key: "createdAt", ascending: true)
]
request.fetchLimit = 40
let frc = NSFetchedResultsController(fetchRequest: request, managedObjectContext: context, sectionNameKeyPath: nil, cacheName: nil)
// fetch only messages with that recipient id of the chat.
let recipientId = "(chat!.recipientId)"
request.predicate = NSPredicate(format: "recipientId == %@", recipientId)
return frc
}()

下面是我如何创建和添加一个新的消息

func createNewTextMessage(recipientId: String, content: String) {
...
guard let id = Int32(recipientId) else { return }
guard let chat = fetchSingleChat(recipientId: id) else { return }
let context = persistentContainer.viewContext
let message = Message(context: context)
let date = Date()
message.chatId = chat.id
message.createdAt = date
message.isRead = false
message.senderId = Int32(currentUserId)
message.senderName = currentUserName
message.senderPhoneNumber = currentUserPhoneNumber
message.status = MessageStatus.unsent.rawValue
message.type = MessageType.text.rawValue
message.owner = MessageOwnerType.mine.rawValue
message.content = content
message.recipientId = chat.recipientId
message.recipientName = chat.title
message.messageId = "(currentUserToken)_(date.millisecondsSince1970)"
// here's where i'm setting some relationship (chat to message: 1-to-many)
message.chat = chat 
chat.lastMessage = message
message.chat?.lastMessage = message
do {
try context.save()
} catch let err {
print("failed to save private chat:", err)
}
}

聊天ManagedObject有一个属性lastMessage，它的类型是Message(也是一个托管对象(，我将新创建的消息设置为聊天的最后一条消息。问题可能来自那里吗。这也是代理代码：

// MARK: - NSFetchedResultsController Delegates
func controllerWillChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
tableView.beginUpdates()
}
func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange sectionInfo: NSFetchedResultsSectionInfo, atSectionIndex sectionIndex: Int, for type: NSFetchedResultsChangeType) {
switch type {
case .insert:
tableView.insertSections(IndexSet(integer: sectionIndex), with: .fade)
case .delete:
tableView.deleteSections(IndexSet(integer: sectionIndex), with: .fade)
case .move:
break
case .update:
break
}
}
func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {
switch type {
case .insert:
tableView.insertRows(at: [newIndexPath!], with: .right)
case .delete:
tableView.deleteRows(at: [indexPath!], with: .fade)
case .update:
tableView.reloadRows(at: [indexPath!], with: .fade)
case .move:
tableView.moveRow(at: indexPath!, to: newIndexPath!)
}
}
func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
tableView.endUpdates()
}

Answer 1

请注意，您对移动行的处理(.move(只移动一行，您应该实现它来移动多行。不确定这是否能解决您的问题，这取决于数据的排序方式。

以下是我如何实现.move

case .move:
if let indexPath = indexPath {
tableView.removeRows(at: IndexSet(integer: indexPath.item), withAnimation: .effectFade)
}
if let newIndexPath = newIndexPath {
tableView.insertRows(at: IndexSet.init(integer: newIndexPath.item), withAnimation: .effectFade)
}