当请求旧数据时，在顶部而不是底部使用fetchedResultsController委托显示tableview的旧消息

Question

目前，我有一个Tableview，它在加载时向Core-Data发送请求，并获取较新消息的前10条消息。

// Initialize Fetch Request
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:@"Chat"];

    // Add Sort Descriptors
    fetchRequest.fetchLimit = 10;
    fetchRequest.predicate = [NSPredicate predicateWithFormat:@"room = %@", _roomid];
    [fetchRequest setSortDescriptors:@[[NSSortDescriptor sortDescriptorWithKey:@"date_message" ascending:NO]]]; // YES;

    // Initialize Fetched Results Controller
    self.fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:nil];

    _fetchedResultsController.delegate = self;

    // Perform Fetch
    NSError *error = nil;
    [self.fetchedResultsController performFetch:&error];

    if (error) {
        NSLog(@"Unable to perform fetch.");
        NSLog(@"%@, %@", error, error.localizedDescription);
    }

在我打电话给他们之后。 消息正确显示在下面。 但是，当我加载（按需获取较旧的消息）时，会使用以下内容。

- (void)fetchOldMessages {

    [self.fetchedResultsController.fetchRequest setSortDescriptors:@[[NSSortDescriptor sortDescriptorWithKey:@"date_message" ascending:NO]]];
    _fetchedResultsController.fetchRequest.fetchLimit +=10;


    NSError *error = nil;
    [self.fetchedResultsController performFetch:&error];

    if (error) {
        NSLog(@"Unable to perform fetch.");
        NSLog(@"%@, %@", error, error.localizedDescription);
    }

    [self.tableView reloadData];

}

问题是旧消息现在显示在下面而不是新消息的上面。 新插入的消息也显示在tableView的顶部而不是底部。

这是我的IndexPath：

- (UITableViewCell*)tableView:(UITableView*)table cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
                Chat *messageInfo = [self.fetchedResultsController objectAtIndexPath:indexPath];

                NSString *CellIdentifier = @"fromMe";
                FromMeTableViewCell *cell = [table dequeueReusableCellWithIdentifier:CellIdentifier];

                cell.message_me.clipsToBounds = YES;
                cell.message_me.layer.cornerRadius = 15;
                cell.message_me.textContainerInset = UIEdgeInsetsMake(8.0, 8.0, 8.0, 8.0);
                cell.message_me.text = messageInfo.message;
                cell.message_date_me.text = [NSString stringWithFormat:@"%@", messageInfo.date_message];

                cell.avatar_message_me.clipsToBounds = YES;
                cell.avatar_message_me.layer.cornerRadius = cell.avatar_message_me.frame.size.width / 2;
                cell.avatar_message_me.image = user_images[@"me"];
                cell.message_me.backgroundColor = [UIColor colorWithRed:0.098 green:0.737 blue:0.611 alpha:1];
                cell.message_me.textColor = [UIColor whiteColor]; //[UIColor whiteColor];

                // Date Settings
                NSDate *today = [[NSDate alloc]init];
                NSDate *message_date = messageInfo.date_message;

                NSDateFormatter  *formatDate = [[NSDateFormatter alloc]init];
                [formatDate setDateFormat:@"yyyy-MM-dd"];

                NSString *today_string = [formatDate stringFromDate:today];
                NSString *message_date_string = [formatDate stringFromDate:message_date];

                // Make Date validation case is older display full date
                if([today_string isEqualToString:message_date_string]){

                    NSDateFormatter *timeformat = [[NSDateFormatter alloc] init];
                    [timeformat setDateFormat:@"hh:mm a"];

                    NSDate *message_date = messageInfo.date_message;
                    NSString *string_date = [timeformat stringFromDate:message_date];
                    cell.message_date_me.text = [NSString stringWithFormat:@"Today at %@",[NSString stringWithFormat:@"%@",string_date]];

                }
                else {
                    NSDateFormatter *timeformat = [[NSDateFormatter alloc] init];
                    [timeformat setDateFormat:@"EEEE d hh:mm a"];

                    NSDate *message_date = messageInfo.date_message;
                    NSString *string_date = [timeformat stringFromDate:message_date];
                    cell.message_date_me.text = [NSString stringWithFormat:@"%@",[NSString stringWithFormat:@"%@",string_date]];
                }

                return cell;


}

这是第一次加载时显示5条消息，但最后一条消息应该关闭，而不是如DATE所示

当我加载更多数据时，它以从新到旧的正确顺序显示消息，但问题是我想在下面显示较新的消息，在上面显示较旧的消息。

Answer 1

使您的提取请求控制器将ASCENDING排序为YES

[self.fetchedResultsController.fetchRequest setSortDescriptors：@ [[NSSortDescriptor sortDescriptorWithKey：@“ date_message”升序：是]]]]；