Question

我正在使用NSFetchedResultsController来填充我的UITableViewController的内容。

我正在使用NSOperation从webService收集数据（我使用的是分离的ManagedObjectContext，因为它是另一个线程）
保存数据时，我的ViewController（NS是NSFetchedResultsControllerDelegate）被调用，我使用mergeChangesFromContextDidSaveNotification合并我的MOC

#pragma mark -
#pragma mark Parsers delegate

- (void)parserWillSave:(id)parser{
    TopNewsParser *emp = (TopNewsParser *)parser;
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(parserContextDidSave:) name:NSManagedObjectContextDidSaveNotification object:emp.managedObjectContext];
    [NSFetchedResultsController deleteCacheWithName:@"aLaUne"];
}

- (void)parserDidSave:(id)parser{
    TopNewsParser *emp = (TopNewsParser *)parser;
    [[NSNotificationCenter defaultCenter] removeObserver:self name:NSManagedObjectContextDidSaveNotification object:emp.managedObjectContext];
}

/**
 Notification from the add controller's context's save operation. This is used to update the fetched results controller's managed object context with the new book instead of performing a fetch (which would be a much more computationally expensive operation).
 */
- (void)parserContextDidSave:(NSNotification*)saveNotification {
    DLog(@"");
    NSManagedObjectContext *fetchContext = [_fetchedResultsController managedObjectContext];
    // Merging changes causes the fetched results controller to update its results
    [fetchContext performSelectorOnMainThread:@selector(mergeChangesFromContextDidSaveNotification:)
                                  withObject:saveNotification
                               waitUntilDone:YES]; 


}

对于NSFetchedResultsControllerDelegate，我正在使用CoreData Books示例中的代码

#pragma mark -
#pragma mark NSFetchedResultsControllerDelegate

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

    [self.tableView beginUpdates];
}


- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath {
    //ALog(@"indexPath: %@ newIndexPath : %@ | type : %d # %@",indexPath,newIndexPath,type,anObject);
    UITableView *tableView = self.tableView;

    switch(type) {

        case NSFetchedResultsChangeInsert:
            [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeDelete:
            [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeUpdate:
            [self configureCell:[tableView cellForRowAtIndexPath:indexPath] atIndexPath:indexPath];
            break;

        case NSFetchedResultsChangeMove:
            [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
            // Reloading the section inserts a new row and ensures that titles are updated appropriately.
            [tableView reloadSections:[NSIndexSet indexSetWithIndex:newIndexPath.section] withRowAnimation:UITableViewRowAnimationFade];
            break;
    }

}


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

    switch(type) {

        case NSFetchedResultsChangeInsert:
            [self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
            break;

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


- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
    UIBarButtonItem *reloadButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemRefresh 
                                                                                  target:self                               
                                                                                  action:@selector(refreshTableViewContent)];
    reloadButton.accessibilityLabel = @"Reload";
    self.navigationItem.leftBarButtonItem = reloadButton;

    // The fetch controller has sent all current change notifications, so tell the table view to process all updates.
    [self.tableView endUpdates];

}

我的问题是当加载新内容时某些对象被删除，我的tableView搞砸了！即使我的countOfRow减少1，该行仍然可见：

然后当我向下滚动我的tableview是空的（只有4个可见的行）仍然在tableview中，否则它是一个空白的scrollView

在控制台中，我可以看到以下消息。

严重的应用程序错误。在调用-controllerDidChangeContent：期间，从NSFetchedResultsController的委托中捕获到异常。 *** - [NSMutableArray removeObjectAtIndex：]：索引0超出userInfo的空数组的边界（null）

在开始尝试时，这是由于我的NSFetchedResultsController的缓存，但即使我禁用它，我也有同样的问题。

有人知道如何解决这个问题吗？

Answer 1

这里也有同样的问题。

人们建议使用TopSongs示例代码。修改版本在这里： http://www.bigbluebrains.com/index.php/2010/08/16/iphone-topsongs-sample-code-memory-leak-fix/

我想知道是否应该在共享数据上使用互斥锁。

刷新和删除后台线程错误中的内容（NSFetchedResultsController）

1 个答案: