ios核心数据：确保从数据源中删除对象

更新：在评论中有人指出我不必要地调度到主线程。在删除调度和不必要的

开始/结束更新之后

，现在当我尝试删除单元格时，它使用case

nsfetchedresultschangediate

（与

nsfetchedresultschangedite

相反）调用

configureCell

使程序崩溃的行是

CollectedLeaf*theCollectedLeaf=[collectionfetchedresultscoontroller objectAtIndexPath:indexPath]在下面的方法中。崩溃日志是，
节列表中索引20处没有节

- (void)configureCell:(SpeciesCell *)cell atIndexPath:(NSIndexPath *)indexPath
{
    CollectedLeaf* theCollectedLeaf = [collectionFetchedResultsController objectAtIndexPath:indexPath];
    [cell setCollectedLeaf:theCollectedLeaf];
}


每次从表中删除单元格时，我都会收到一个
无效更新：节中的行数无效
错误。我在
controllerDidChangeContent
中的
[\u table endUpdates]
处获得断点

在许多SO POST中，出现此错误的原因是，在从表中删除行之前，对象尚未从数据源中删除。我在
committeeditingstyle
中从数据源中删除对象，该对象在
didChangeObject
中的
deleteRowsAtIndexPaths
之前调用

尽管我下了命令，但我仍然得到
无效更新
，这一事实让我认为我没有正确/成功地从数据源中删除它。我还是iOS新手-如何确保从我的核心数据中删除对象

- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller
{
    // The fetch controller is about to start sending change notifications, so prepare the table view for updates.
    [_table beginUpdates];
}

- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject
       atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type
      newIndexPath:(NSIndexPath *)newIndexPath {
    switch(type) {

        case NSFetchedResultsChangeInsert:
            [_table beginUpdates];

            [_table insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]
                          withRowAnimation:UITableViewRowAnimationFade];
            [_table endUpdates];
            break;

        case NSFetchedResultsChangeDelete:
            NSLog(@"delete called");
            [_table deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath]
                          withRowAnimation:UITableViewRowAnimationFade];


            break;

        case NSFetchedResultsChangeUpdate:
           // [self configureCell:[_table cellForRowAtIndexPath:indexPath]
                   // atIndexPath:indexPath];
            [_table reloadRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
            NSLog(@"fetched update");
            break;

        case NSFetchedResultsChangeMove:
            [_table deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath]
                          withRowAnimation:UITableViewRowAnimationFade];
            [_table insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]
                          withRowAnimation:UITableViewRowAnimationFade];
            break;
    }
}

- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type
{
    switch(type)
    {
        case NSFetchedResultsChangeInsert:
            [_table insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeDelete:
            [_table deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
            break;
        case NSFetchedResultsChangeMove:
            break;
        case NSFetchedResultsChangeUpdate:
            break;
    }
}

- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller
{
    [_table endUpdates];
}
-(UITableViewCellEditingStyle)tableView:(UITableView *)tableView editingStyleForRowAtIndexPath:(NSIndexPath *)indexPath
{
    if(_segmentedControl.selectedSegmentIndex == 1) {
        NSLog(@"index path at editingStyleForRowAtIndexPath %@", indexPath);
        return UITableViewCellEditingStyleDelete;
    }
    return NULL;
}

- (void)tableView:(UITableView*)tableView didEndEditingRowAtIndexPath:(NSIndexPath *)indexPath
{
    // [super tableView: tableView didEndEditingRowAtIndexPath:indexPath];
    if(_segmentedControl.selectedSegmentIndex == 1) {
        for (UITableViewCell *cell in [_table visibleCells]) {
            for (UIView *subview in cell.contentView.subviews)
                [subview.layer removeAllAnimations];
        }
    }
}
// Override to support editing the table view.
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
    /*Only allow deletion for collection table */
    if(_segmentedControl.selectedSegmentIndex == 1) {
        if (editingStyle == UITableViewCellEditingStyleDelete)
        {
            NSLog(@"index path at commitediting style %@", indexPath);
            CollectedLeaf* collectedLeaf = [collectionFetchedResultsController objectAtIndexPath:indexPath];
            LeafletPhotoUploader * leafletPhotoUploader = [[LeafletPhotoUploader alloc] init];
            leafletPhotoUploader.collectedLeaf = collectedLeaf;

            if([LeafletUserRegistration isUserRegistered]) {
                [leafletPhotoUploader deleteCollectedLeaf:collectedLeaf delegate:self];
            }

            // Delete the managed object for the given index path
            NSManagedObjectContext *context = [collectionFetchedResultsController managedObjectContext]; 
                [context deleteObject:[collectionFetchedResultsController objectAtIndexPath:indexPath]];

            // Save the context.
            NSError *error;
            if (![context save:&error])
            {
                NSLog(@"Failed to save to data store: %@", [error localizedDescription]);
                NSArray* detailedErrors = [[error userInfo] objectForKey:NSDetailedErrorsKey];
                if(detailedErrors != nil && [detailedErrors count] > 0)
                {
                    for(NSError* detailedError in detailedErrors)
                    {
                        NSLog(@"  DetailedError: %@", [detailedError userInfo]);
                    }
                }
                else
                {
                    NSLog(@"  %@", [error userInfo]);
                }
            }
        }
    }
}
// Customize the appearance of table view cells.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"speciesCell";

    SpeciesCell* speciesCell = (SpeciesCell*)[tableView dequeueReusableCellWithIdentifier:CellIdentifier];

    [self configureCell:speciesCell atIndexPath:indexPath];
    speciesCell.labelCheckMark.backgroundColor = [UIColor blackColor];

    return speciesCell;
}
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {

    return 1;
}
- (NSInteger) tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{

    id <NSFetchedResultsSectionInfo> sectionInfo = [[collectionFetchedResultsController sections] objectAtIndex:section];
    if([sectionInfo numberOfObjects] == 0){
        UILabel *noDataLabel         = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, tableView.bounds.size.width, tableView.bounds.size.height)];
        noDataLabel.text             = @"Press the Snap It! tab to start collecting!";
        //Start your collection by tapping on the Snap It! tab.";
        noDataLabel.textColor        = [UIColor whiteColor];
        noDataLabel.textAlignment    = NSTextAlignmentCenter;
        tableView.backgroundView = noDataLabel;
        tableView.separatorStyle = UITableViewCellSeparatorStyleNone;
    }
    return [sectionInfo numberOfObjects];
}

-（void）controllerWillChangeContent:（NSFetchedResultsController*）控制器
{
//fetch控制器即将开始发送更改通知，因此请准备表视图以进行更新。
[_表开始更新]；
}
-（void）控制器：（NSFetchedResultsController*）控制器didChangeObject:（id）一个对象
atIndexPath:（NSIndexPath*）indexPath forChangeType:（NSFetchedResultsChangeType）类型
newindepath:（nsindepath*）newindepath{
开关（类型）{
案例NSFetchedResultsChangesInsert：
[_表开始更新]；
[_tableinsertrowsatindexpath:[NSArray arrayWithObject:newIndexPath]
withRowAnimation:UITableViewRowAnimationFade]；
[_tableendupdates]；
打破
案例NSFetchedResultsChangeDelete：
NSLog（@“删除调用”）；
[_tabledeleteRowsatindExpath:[NSArray arrayWithObject:indexPath]
withRowAnimation:UITableViewRowAnimationFade]；
打破
案例NSFetchedResultsChangeUpdate：
//[自配置单元格：[[表单元格FORROWATINDEXPATH:indexPath]
//atIndexPath:indexath]；
[_tablereloadrowsatindexpath:@[indexath]with rowanimation:UITableViewRowAnimationAutomatic]；
NSLog（@“获取的更新”）；
打破
案例NSFetchedResultsChangeMove：
[_tabledeleteRowsatindExpath:[NSArray arrayWithObject:indexPath]
withRowAnimation:UITableViewRowAnimationFade]；
[_tableinsertrowsatindexpath:[NSArray arrayWithObject:newIndexPath]
withRowAnimation:UITableViewRowAnimationFade]；
打破
}
}
-（void）控制器：（NSFetchedResultsController*）控制器didChangeSection:（id）sectionInfo atIndex:（nsInteger）ChangeType的sectionIndex:（NSFetchedResultsChangeType）类型
{
开关（类型）
{
案例NSFetchedResultsChangesInsert：
[_tableinsertSections:[NSIndexSet IndexSetWithiIndex:sectionIndex]with RowAnimation:UITableViewRowAnimationFade]；
打破
案例NSFetchedResultsChangeDelete：
[_tabledeleteSections:[NSIndexSet indexetwithindex:sectionIndex]withRowAnimation:UITableViewRowAnimationFade]；
打破
案例NSFetchedResultsChangeMove：
打破
案例NSFetchedResultsChangeUpdate：
打破
}
}
-（void）controllerDidChangeContent:（NSFetchedResultsController*）控制器
{
[_tableendupdates]；
}
-（UITableViewCellEditingStyle）tableView:（UITableView*）tableView editingStyleForRowAtIndexPath:（NSIndexPath*）indexPath
{
如果（_segmentedControl.selectedSegmentIndex==1）{
NSLog（@“EditingStyleForRowatingIndexPath%@”处的索引路径，indexPath）；
返回UITableViewCellEditingStyleDelete；
}
返回NULL；
}
-（void）tableView:（UITableView*）tableView diddeditingrowtaindexpath:（nsindepath*）indepath
{
//[super tableView:tableView didendeditingrowtaindexpath:indexath]；
如果（_segmentedControl.selectedSegmentIndex==1）{
对于（UITableViewCell*单元格在[\u表visibleCells]中）{
用于（UIView*cell.contentView.subview中的子视图）
[subview.layer removeAllAnimations]；
}
}
}
//替代以支持编辑表格视图。
-（void）tableView:（UITableView*）tableView提交的编辑样式：（UITableViewCellEditingStyle）行的编辑样式索引路径：（NSIndexPath*）索引路径
{
/*仅允许删除集合表*/
如果（_segmentedControl.selectedSegmentIndex==1）{
如果（editingStyle==UITableViewCellEditingStyleDelete）
{
NSLog（@“提交样式的索引路径%@”，indexath）；
CollectedLeaf*CollectedLeaf=[collectionFetchedResultsController对象索引路径：indexPath]；
传单照片上传器*传单照片上传器=[[传单照片上传器alloc]init]；
传单Photouploader.collectedLeaf=collectedLeaf；
如果（[传单用户注册为用户注册]）{
[传单照片上载器删除collectedLeaf:collectedLeaf代理：self]；
}
//删除给定索引路径的托管对象
NSManagedObjectContext*上下文=[collectionFetchedResultsController managedObjectContext]；
[上下文删除对象：[collectionFetchedResultsController对象索引路径：indexPath]]；
    CollectedLeaf* theCollectedLeaf = nil;
    if ([[collectionFetchedResultsController sections] count] > [indexPath section]){
        id <NSFetchedResultsSectionInfo> sectionInfo = [[collectionFetchedResultsController sections] objectAtIndex:[indexPath section]];
        if ([sectionInfo numberOfObjects] > [indexPath row]){
            theCollectedLeaf = [collectionFetchedResultsController objectAtIndexPath:indexPath];

        //do whatever else I need, delete the object, etc
        }

    }