iOS8 swift : deleteRowsAtIndexPaths crashes

Question

我在 Swift、iOS 8、Xcode 6 Beta 6 中从我的 tableView 中删除一行时遇到了一些麻烦。每次我尝试删除一行时，我都会收到类似

的错误

Assertion failure in -[UITableView _endCellAnimationsWithContext:], /SourceCache/UIKit_Sim/UIKit-3302.3.1/UITableView.m:1581 2014-08-30 20:31:00.971 Class Directory[13290:3241692] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Invalid update: invalid number of rows in section 1. The number of rows contained in an existing section after the update (25) must be equal to the number of rows contained in that section before the update (25), plus or minus the number of rows inserted or deleted from that section (0 inserted, 1 deleted) and plus or minus the number of rows moved into or out of that section (0 moved in, 0 moved out).

我已经阅读了这个常见问题的所有答案，在这里，我觉得我已经满足了推荐的条件。项目似乎要从数据模型中删除 - - 当我重新加载应用程序时，已删除的项目从表中消失了 - 但相应的 sqlite 文件中似乎有一些残留物，当然数学不会加起来。输出 indexPath 的 println 显示了正确的 Section 和 Row。我很疑惑。这应该很简单，但我确信我遗漏了一些愚蠢的东西，我怀疑是在数据模型删除中。完整项目 Github .

func numberOfSectionsInTableView(tableView: UITableView!) -> Int {

    return fetchedResultController.sections.count

}


func tableView(tableView: UITableView!, numberOfRowsInSection section: Int) -> Int {
    return fetchedResultController.sections[section].numberOfObjects

    }

func tableView(tableView: UITableView!, cellForRowAtIndexPath indexPath: NSIndexPath!) -> UITableViewCell! {
    let cell = tableViewMain.dequeueReusableCellWithIdentifier("CellMain", forIndexPath: indexPath) as UITableViewCell

        let personForRow = fetchedResultController.objectAtIndexPath(indexPath) as Person
        cell.textLabel.text = personForRow.fullName()

        return cell

}

func tableView(tableView: UITableView!, canEditRowAtIndexPath indexPath: NSIndexPath!) -> Bool {
    return true
}

func tableView(tableView: UITableView!, editingStyleForRowAtIndexPath indexPath: NSIndexPath!) -> UITableViewCellEditingStyle {
    return UITableViewCellEditingStyle.Delete
}

 func tableView(tableView: UITableView!, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath!) {
    println("section and row \(indexPath.section) \(indexPath.row) ")
    if (editingStyle == UITableViewCellEditingStyle.Delete) {
    let personForRow : NSManagedObject = fetchedResultController.objectAtIndexPath(indexPath) as Person
    context?.deleteObject(personForRow)
    context?.save(nil)
        tableViewMain.beginUpdates()
    tableViewMain.deleteRowsAtIndexPaths([indexPath], withRowAnimation: UITableViewRowAnimation.Fade)
        tableViewMain.endUpdates()
    }

Answer 1

使用 Xcode Core Data Master-Detail 模板项目可以轻松重现崩溃。作为一般规则，当您使用 NSFetchedResultsController 时，您应该真正使用 NSFetchedResultsControllerDelegate(您已声明但不使用它)。

删除 tableView:commitEditingStyle:forRowAtIndexPath: 方法中的那些行:

tableViewMain.beginUpdates()
tableViewMain!.deleteRowsAtIndexPaths([indexPath!], withRowAnimation: UITableViewRowAnimation.Fade)
tableViewMain.endUpdates()

并将这些行添加到您的 viewController 类中:

func controllerWillChangeContent(controller: NSFetchedResultsController) {
    tableViewMain.beginUpdates()
}

func controller(controller: NSFetchedResultsController!, didChangeSection sectionInfo: NSFetchedResultsSectionInfo!, atIndex sectionIndex: Int, forChangeType type: NSFetchedResultsChangeType) {
    switch type {
    case .Insert:
        tableViewMain.insertSections(NSIndexSet(index: sectionIndex), withRowAnimation: .Fade)
    case .Delete:
        tableViewMain.deleteSections(NSIndexSet(index: sectionIndex), withRowAnimation: .Fade)
    default:
        return
    }
}

func controller(controller: NSFetchedResultsController!, didChangeObject anObject: AnyObject!, atIndexPath indexPath: NSIndexPath!, forChangeType type: NSFetchedResultsChangeType, newIndexPath: NSIndexPath!) {
    switch type {
    case .Insert:
        tableViewMain.insertRowsAtIndexPaths([newIndexPath], withRowAnimation: .Fade)
    case .Delete:
        tableViewMain.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
    case .Update:
        return
        //Should also manage this case!!!
        //self.configureCell(tableView.cellForRowAtIndexPath(indexPath), atIndexPath: indexPath)
    case .Move:
        tableViewMain.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
        tableViewMain.insertRowsAtIndexPaths([newIndexPath], withRowAnimation: .Fade)
    default:
        return
    }
}

func controllerDidChangeContent(controller: NSFetchedResultsController!) {
    tableViewMain.endUpdates()
}

这应该可以解决您的问题。