ios - 奇妙なバグ: NSFetchedResultsController 内の NSPredicate のコメントを外すと、UITableView が空になります

Question

奇妙なバグがあります: のコメントを外すNSPredicateと、結果UITableViewは空になります。

私のデータモデルは次のとおりです: カテゴリ <-->> フィード <-->> 投稿

sを取得していPostます。Post.feedです。Post_ プロパティを持っています。FeedFeedrss NString

コードは次のとおりです。

    - (NSFetchedResultsController *)fetchedResultsController {

        // Set up the fetched results controller if needed.
        if (_fetchedResultsController == nil) {
            // Create the fetch request for the entity.
            NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
            // Edit the entity name as appropriate.
            NSEntityDescription *entity = [NSEntityDescription entityForName:@"Post"
                                                      inManagedObjectContext:_globalMOC];
            [fetchRequest setEntity:entity];

            // Edit the sort key as appropriate.
            NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"date" ascending:NO];
            NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
            [fetchRequest setSortDescriptors:sortDescriptors];

            NSPredicate *predicate =[NSPredicate predicateWithFormat:@"feed.rss == %@",  _detailItem.rss];
            [fetchRequest setPredicate:predicate];

            // Edit the section name key path and cache name if appropriate.
            // nil for section name key path means "no sections".
            NSFetchedResultsController *aFetchedResultsController =
            [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest
                                                managedObjectContext:_globalMOC
                                                  sectionNameKeyPath:nil
                                                           cacheName:nil];
            self.fetchedResultsController = aFetchedResultsController;

            self.fetchedResultsController.delegate = self;

            NSError *error = nil;

            if (![self.fetchedResultsController performFetch:&error]) {
                // Replace this implementation with code to handle the error appropriately.
                // abort() causes the application to generate a crash log and terminate.
                // You should not use this function in a shipping application, although it may be useful
                // during development. If it is not possible to recover from the error, display an alert
                // panel that instructs the user to quit the application by pressing the Home button.
                //
                NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
                abort();
            }

        }

        return _fetchedResultsController;
    }

のコメントを外した場合にのみ結果が表示されますNSPredicate。、、、を二重引用符と一重引用符で囲んでLIKEみ==ました...=%@

Feedオブジェクトを直接比較するのが最善です...

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