Question

需要提示，在花费几个小时与NSFetchedResultsController挣扎后放弃。

错误消息是：

CoreData：错误：NSFetchedResultsController：索引处没有对象 2147483647在索引0的部分

...但我甚至不知道是谁解雇了这个错误。我的代码的最后一部分是saveContext（），下一个断点在didChange内。

class ViewController : UITableViewController, NSFetchedResultsControllerDelegate
private lazy var channelController: NSFetchedResultsController<ZChannel> = {

    let appDelegate: AppDelegate = UIApplication.shared.delegate as! AppDelegate

    let request: NSFetchRequest<ZChannel> = ZChannel.fetchRequest()
    request.sortDescriptors = [NSSortDescriptor(key: "kit", ascending: true), NSSortDescriptor(key: "name", ascending: true)]

    let retval: NSFetchedResultsController<ZChannel> = NSFetchedResultsController(fetchRequest: request,
                                                                                 managedObjectContext: appDelegate.persistentContainer.viewContext,
                                                                                 sectionNameKeyPath: "kit",
                                                                                 cacheName: nil)
    retval.delegate = self

    return retval
}()

public init() {
    super.init(style: .grouped)

    self.tableView.register(ChannelTableCell.self, forCellReuseIdentifier: "ChannelTableCell")

    let appDelegate: AppDelegate = UIApplication.shared.delegate as! AppDelegate
    appDelegate.persistentContainer.viewContext.perform {
        do {
            try self.channelController.performFetch()
        } catch {
            let e = error as NSError
            fatalError("[CoreData] Unresolved fetch error \(e), \(e.userInfo)")
        }
    }
}   


public func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {
    switch(type) {
    case .insert:
        self.tableView?.insertRows(at: [newIndexPath!], with: .bottom)
        break;
    case .update:
        self.tableView?.reloadRows(at: [indexPath!], with: .bottom)
        break
    default:
        break
    }
}

public func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange sectionInfo: NSFetchedResultsSectionInfo, atSectionIndex sectionIndex: Int, for type: NSFetchedResultsChangeType) {
    switch (type) {
    case .insert:
        self.tableView?.insertSections(IndexSet(integer: sectionIndex), with: UITableViewRowAnimation.bottom)
        break
    case .delete:
        self.tableView?.deleteSections(IndexSet(integer: sectionIndex), with: UITableViewRowAnimation.bottom)
        break
    default:
        break
    }
}

从另一个线程我插入新对象：

self.persistentContainer.viewContext.performAndWait
{
    // ...
    let channel: ZChannel = NSEntityDescription.insertNewObject(forEntityName: "ZChannel", into: self.persistentContainer.viewContext) as! ZChannel
    // ...
    self.saveContext()
}

Answer 1

一些问题：

2147483647是NSNotFound。如果您正在使用indexOfObject之类的内容并假设它在数组中，然后使用可能导致崩溃的索引。
当您应该使用newIndexPath时，您正在使用indexPath进行行更新。原因是indexPath是任何insert或delete之前的索引，newIndexPath是插入和删除之后的索引。
没有理由在self.channelController.performFetch()内调用您已经在主线程上的persistentContainer.viewContext.perform

NSFetchedResultsController：索引2147483647没有对象

1 个答案: