删除部分中的最后一行 - >崩溃，使用NSFetchedResultsController [英] Deleting last row in a section -> crash, using NSFetchedResultsController

问题描述

我正在使用NSFetchedResultsController。以前我有一个类似的问题，当数据库没有tableview的条目，但后来创建一个，我发现必须至少有一个部分，所以我修复了。但是现在它崩溃了，例如我有两个部分，每个部分有一行，我删除了一行，所以部分应该消失 - >崩溃。它表示更新前的部分数量（2）不等于删除的数量（0）。

I'm using NSFetchedResultsController. Previously I had a similar issue when the database has no entries for the tableview but then one is created, I turned out there has to be at least one section, so I fixed that. But now it crashes when I have for example two sections, each with one row and I delete one row, so section should be gone -> crash. It says that the number of sections before the update (2) is not equal to the number deleted (0).

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    // Return 1 if the fetchedResultsController section count is zero
    return [[fetchedResultsController sections] count] ? : 1;
}

- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {
    // check if we really have any sections in the managed object:
    if (!fetchedResultsController.sections.count) return @"Persoonlijk";

    id <NSFetchedResultsSectionInfo> sectionInfo = [[fetchedResultsController sections] objectAtIndex:section];
    return [sectionInfo name];
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    // check if we really have any sections in the managed object:
    if (!fetchedResultsController.sections.count) return 0;

    id <NSFetchedResultsSectionInfo> sectionInfo = [[fetchedResultsController sections] objectAtIndex:section];
    return [sectionInfo numberOfObjects];
}

更新
行获取的方法删除：

Update Method where row gets deleted:

- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {
    if (editingStyle == UITableViewCellEditingStyleDelete) {
        // Delete schedule
        NSManagedObjectContext *context = [fetchedResultsController managedObjectContext];
        [context deleteObject:[fetchedResultsController objectAtIndexPath:indexPath]];

        // Save the context.
        NSError *error = nil;
        if (![context save:&error]) {
            NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
            exit(-1);
        }
   } 
}

推荐答案

我发现问题/解决方案：

I found the problem/solution:

我没有针对这种情况所需的didChangeSection委托方法！

I did not have the required didChangeSection delegate method for this situation!

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

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

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

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