NSFetchedResultsController的节数无效

问题描述

我正在使用NSFetchedResultsController来管理tableView数据源，但是当我尝试添加实体时，它一直崩溃，这给了我这个错误： Terminating app due to uncaught exception 'NSInternalInconsistencyException',reason: 'Invalid update: invalid number of sections. The number of sections contained in the table view after the update (1) must be equal to the number of sections contained in the table view before the update (0),plus or minus the number of sections inserted or deleted (0 inserted,0 deleted).'

执行此代码时发生错误：

let exercisetoAdd = Workout_Exercise(context: DataController.shared.context)
        exercisetoAdd.name = exercise
        exercisetoAdd.exerciseIndex = Int16((currentWorkout?.exercises?.allObjects.count)! + 1)
        let firstemptySet = CDSet(context: DataController.shared.context)
        exercisetoAdd.addToSets(firstemptySet)
        currentWorkout.addToExercises(exercisetoAdd)

为实体CDSet设置了NSFetchedResultsController，我敢肯定我已经拥有所有必需的协议存根：

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 .insert:
        tableView.insertRows(at: [newIndexPath!],with: .fade)
    case .delete:
        tableView.deleteRows(at: [newIndexPath!],with: .fade)
    default:
        break
    }
}

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

func tableView(_ tableView: UITableView,numberOfRowsInSection section: Int) -> Int {
    if let rows = fetchedResultsController.sections?[section].numberOfObjects {
        return rows
    } else {
        return 0
    }
}

这是我正在使用的提取请求：

    let fetchRequest:NSFetchRequest<CDSet> = CDSet.fetchRequest()
    fetchRequest.sortDescriptors = [NSSortDescriptor(key: "exercise",ascending: false)]
    fetchRequest.predicate = nspredicate(format: "exercise.workout == %@",currentWorkout)
    
    fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest,managedobjectContext: DataController.shared.context,sectionNameKeyPath: "exercise",cacheName: nil)
    fetchedResultsController.delegate = self
    
    do {
        try fetchedResultsController.performFetch()
    } catch {
        
    }

我不知道是什么原因导致了错误的发生，有人遇到过类似的问题并能够找到解决方案吗？

解决方法

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