Question

I am trying to create an application that has two UITableViews placed side-by-side. The left one lists article categories and the right one displays article previews (kind of like flipboard’s search view).

On the left tableview’s didSelectRowAtIndexPath, I am supposed to download the article and display the previews on the right UITableView. However, I cannot seem to make this work.

My assumption is that I reload the data on the tableview before the download is finished. Any suggestions?

EDITED:

Here’s my current code:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) 
    {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
        if (tableView.tag == 1) 
        { 
            //if it's the left tableView (no problem here)
            NSDictionary *catDic = [[Category categories] objectAtIndex:indexPath.row];
            cell.textLabel.text = [catDic valueForKey:@"name"];
            cell.textLabel.font = [UIFont fontWithName:@"HelveticaNeue-Bold" size:[UIFont labelFontSize]];
        }

        if (tableView.tag == 2) 
        { 
            //if it's the right tableView
            ArticlePreview *articleView = [[ArticlePreview alloc] initFlexibleHeightRowForArticleInfo:[self.articleInfos objectAtIndex:indexPath.row]]; 
            //ArticlePreview is a custom class that create the articlePreview view, 
            //articleInfos is a variable that holds the articles in core data
            [cell.contentView addSubview:articleView];
            [articleView release];
        }
    }

    return cell;
}

-(void) loadArticlePreview: (NSNumber *)_idx
{
    [Category downloadArticlesforIndex:[_idx intValue]];

    AppDelegate *delegate = [[UIApplication sharedApplication] delegate];
    NSManagedObjectContext *context = [delegate managedObjectContext];

    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"ArticleInfo" inManagedObjectContext:context];
    [fetchRequest setEntity:entity];
    NSError *error;
    self.articleInfos = [context executeFetchRequest:fetchRequest error:&error];

    [fetchRequest release];

    [self.articlePreviewTableView reloadData]; 
    //articlePreviewTableView is the right table view identifier, hooked with IBOutlet and all
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (tableView.tag == 1) //if it's the left table
    {
        [self performSelectorInBackground:@selector(loadArticlePreview:) withObject:[NSNumber numberWithInt:indexPath.row]];
    }
}

The problem is that the right tableview does not refresh. I think these methods are where the problem probably is.

Answer 1

According to your code, if you dequeue a UITableViewCell, its going to use the old cell, without any modifications for the actual cell that you need. Change it to so:

UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) 
    {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
}//after this, use the tableView tag to identify.

You are also adding a content view to the preview table cell. I strongly recommend you create a custom UITableViewCell class when you do this. I found that to be the only way the adding subviews works in cells and is a lot easier to manage the cells with the custom class.

I assume you are doing the downloading in some method in the ArticlePreview. You don’t need to reload the tableView once the download is finished. Since the ArticlePreview object has been added as the cell’s subview, when the download is finished in it, call setNeedsDisplay when the view is content is downloaded.