我几乎尝试了一切，但无法弄清楚出了什么问题。我有一个 NSFetchedResultsController 并从核心数据中获取一些帖子。然后我有一种方法可以将新帖子插入到相同的上下文中并保存上下文。通常，didChangeObject: 方法现在应该被调用，但它不会。我有一个类似的视图控制器，我在不同的表（=nsmanaged 对象）上基本相同，并且 didChangeObject: 方法被成功调用。
到目前为止我已经尝试过：
为这个视图控制器创建了另一个上下文
移除了 NSFetchedResultsController 的缓存
以下方法从核心数据数据库中提取数据并将其“存储”到 NSFetchedResultsController（变量：）controller中。
//reloading newsgroups from coredata
- (void)reloadNewsgroupsFromCoreData
{
//creating fetch request
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:@"Post"];
//sorting by transient date (hour and secons cutted off)
NSSortDescriptor *sortByDate = [[NSSortDescriptor alloc] initWithKey:@"dateCreatedTransient" ascending:NO];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortByDate, nil];
[fetchRequest setSortDescriptors:sortDescriptors];
//where clause
[fetchRequest setPredicate:[NSPredicate predicateWithFormat:@"ref_subscribed_newsgroup == %@ AND references == nil", self.newsgroup]];
//setting fetchrequest
self.controller = [[NSFetchedResultsController alloc]
initWithFetchRequest:fetchRequest
managedObjectContext:self.context
sectionNameKeyPath:@"dateCreatedForSections"
cacheName:nil]; //todo, maybe add a cache here!
//fetch
NSError *error;
[self.controller performFetch:&error];
if (error) {
NSLog(@"%@", error);
}
}
此外，根据文档，我将 NSFetchedResultsController 的委托设置为我的视图控制器（这与上述 fetch 方法所在的位置相同）。
在viewDidLoad：
self.controller.delegate = self;
然后我实现了协议中的方法，也是didChangeObject:
- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath {
UITableView *tableView = self.tableView;
// I HAVE ADDED A BREAKPOINT HERE BUT IT NEVER STOPS HERE.
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];
[tableView insertRowsAtIndexPaths:[NSArray
arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
}
}
然后我有另一种方法将一些帖子存储到核心数据中。我认为这很重要：这个方法是通过另一个线程的委托调用的。（服务器连接使用 调用它performSelectorOnMainThread:...）
- (void)storeIntoCoreData:(NSArray*)postsArray
{
...
Post *entity = [NSEntityDescription insertNewObjectForEntityForName: @"Post" inManagedObjectContext:context];
entity.inReply = dummy.in_reply;
entity.body = dummy.body;
entity.email = dummy.email;
entity.from = dummy.from;
entity.messageIdentifier = dummy.message_identifier;
entity.references = dummy.references;
entity.subject = dummy.subject;
entity.dateCreated = dummy.date;
entity.unread = [NSNumber numberWithInt:1];
...
[self.context save:&error];
if (error)
{
NSLog(@"error: %@", error);
}
// IMPORTANT: CURRENTLY I AM CALLING THIS METHOD AGAIN HERE, WHICH
// FETCHES ALL POSTS OUT OF CORE DATA.
// THIS IS SO UGLY AND NOT PERFORMANT.
// THEN I INVOKE RELOADDATA ON THE TABLEVIEW TO RELOAD THE ENTIRE TABLE
// BUT THERE WAS JUST ONE INSERT SO A ENTIRE RELOAD WOULD NOT BE NECESSARY.
[self reloadNewsgroupsFromCoreData];
[self.tableView reloadData];
// I HAVE TO DO THIS BECAUSE THE didChangeObject METHOD GETS NOT CALLED.
}
有没有人有提示或建议可能有什么问题？
谢谢和问候， 克里斯