Question

我的数据库模型有一个MainCategory实体和一个SpendingCategory实体。这里我按MainCategory.position分组。但是如果这些位置发生了变化，NSFetchedResultsController的结果就不会发生变化。如何使用此FetchedResultsController跟踪这些更改？

    self.managedObjectContext = ((AppDelegate *)[[UIApplication sharedApplication] delegate]).managedObjectContext;

    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"SpendingCategory"];

    NSSortDescriptor *mainCatPosition = [[NSSortDescriptor alloc]
                            initWithKey:@"belongsToMainCategory.position" ascending:YES];
    NSSortDescriptor *spendingCatPosition = [[NSSortDescriptor alloc]
                            initWithKey:@"position" ascending:YES];

    request.sortDescriptors = [NSArray arrayWithObjects:mainCatPosition,spendingCatPosition,nil];
    request.predicate = [NSPredicate predicateWithFormat:@"liveBudget = %@", [NSNumber numberWithBool:YES]];

    self.fetchedResultsController = [[NSFetchedResultsController alloc]initWithFetchRequest:request
                                                                       managedObjectContext:self.managedObjectContext
                                                                         sectionNameKeyPath:@"belongsToMainCategory.position"
                                                                                  cacheName:nil];

修改：

- (void)controller:(NSFetchedResultsController *)controller
  didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo
           atIndex:(NSUInteger)sectionIndex
     forChangeType:(NSFetchedResultsChangeType)type
{
    if(!self.reordering){
        if (!self.suspendAutomaticTrackingOfChangesInManagedObjectContext)
        {
            switch(type)
            {
                case NSFetchedResultsChangeInsert:
                    [self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
                    break;

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

Answer 1

您必须实施NSFetchedResultsControllerDelegate。实现专门处理部分的回调：

controller:didChangeSection:atIndex:forChangeType:

NSFetchedResultsController：sectionNameKeyPath没有跟踪更改？

1 个答案: