删除行时应用程序崩溃

Question

我的表用于列出核心数据中的行。一切正常，我使用了两种类型的数据加载到同一个表视图上。数据类型会因范围按钮的变化而变化。两个范围按钮，一个显示已完成的任务，另一个显示待处理的任务。我可以在桌子上搜索、更新。虽然只有完整的数据列表是可编辑和可以删除的，但有时它工作正常，有时会给出错误，

Serious application error.  An exception was caught from the delegate of 
NSFetchedResultsController during a call to -controllerDidChangeContent:.  *** -
[NSMutableArray insertObject:atIndex:]: index 4 beyond bounds for empty array with 
userInfo (null)

获取结果控制器初始化为，

- (NSFetchedResultsController *)fetchedResultsControllerWithPredicate:(NSPredicate *)predicate{

if (self.fetchedResultsControl != nil) {
    NSLog(@"Here I am outside");

    return self.fetchedResultsControl;

}

加载表视图单元格的代码如下：

   - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

static NSString *CellIdentifier = @"Cell";

CustomCell *cell =(CustomCell *) [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
    NSArray *topLevelObjects=[[NSBundle mainBundle] loadNibNamed:@"CustomCell" owner:nil options:nil];
    for (id currentObject in topLevelObjects) {
        if([currentObject isKindOfClass:[UITableViewCell class]]){
            cell=(CustomCell *)currentObject;
            break;
        }
    }

}

[self configureCell:cell atIndexPath:indexPath];
return cell;

}

并且更新方法称为通过 NSFetchedResultsControllerDelegate 如下：

- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller {
[self.listingTable beginUpdates];
NSLog(@"Changed content");
}

- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <  NSFetchedResultsSectionInfo>)sectionInfo
       atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type {

switch(type) {
    case NSFetchedResultsChangeInsert:
        [self.listingTable insertSections:[NSIndexSet indexSetWithIndex:sectionIndex]
                      withRowAnimation:UITableViewRowAnimationFade];
        break;

    case NSFetchedResultsChangeDelete:
        [self.listingTable deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex]
                      withRowAnimation:UITableViewRowAnimationFade];
        break;
}

}

- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject
   atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type
  newIndexPath:(NSIndexPath *)newIndexPath {
NSLog(@"Changed content switch case");
UITableView *tableView = self.listingTable;

switch(type) {

    case NSFetchedResultsChangeInsert:
        [self.listingTable insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]
                         withRowAnimation:UITableViewRowAnimationTop];
        break;

    case NSFetchedResultsChangeDelete:
        [self.listingTable deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath]
                         withRowAnimation:UITableViewRowAnimationFade];
        break;

    case NSFetchedResultsChangeUpdate:
        [self configureCell:(CustomCell *)[tableView  cellForRowAtIndexPath:indexPath]
                atIndexPath:indexPath];

        break;

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


- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
NSLog(@"Changed Content");
[self.listingTable endUpdates];

}

Answer 1

我没有看到任何明显的错误，但在一个表视图中交换两个逻辑表是一种危险的设计，因为你必须非常小心，表视图知道它的逻辑表已被更改。

您收到的错误表明表视图正在使用一个逻辑表的索引之一来配置自身，但实际上正在访问第二个逻辑表的数组，该数组较短。

您的直接解决方案是仔细查看 numberOfSections 和 numberOfRowsInSection 等方法，以确保在切换逻辑表时这些方法正确更新。

最好的设计解决方案是使用两个单独的表视图及其自己单独的数据源，然后根据需要交换它们。