我几乎尝试了所有方法，但无法找出问题所在。我有一个 NSFetchedResultsController 并从核心数据中获取一些帖子。然后我有一个方法，可以将新帖子插入到同一上下文中并保存上下文。通常，现在应该调用 didChangeObject: 方法，但事实并非如此。我有一个类似的视图控制器，我在不同的表（=ns Managed 对象）上执行基本相同的操作，并且 didChangeObject: 方法被成功调用。
到目前为止我已经尝试过：
以下方法从核心数据数据库中提取数据并将其“存储”到 NSFetchedResultsController 中（变量：controller).
//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（这与前面提到的 fetch 方法所在的位置相同）。
In viewDidLoad:
self.controller.delegate = self;
然后我实现了协议中的方法，还有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：该方法是通过另一个线程的委托调用的。 （服务器连接使用它调用它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.
}
有人有什么提示或建议可能是错误的吗？
感谢致敬，
克里斯
