Populating NSImage with data from an asynchronous NSURLConnection

Question

I have hit the proverbial wall trying to figure out how to populate an NSImage with data returned from an asynchronous NSURLConnection in my desktop app (NOT an iPhone applicati

Answer 1

Your intuition is correct; you want to have a callback from the object which is the NSURLConnection’s delegate to the controller which manages the table view, which would update your data source and then call -setNeedsDisplayInRect: with the rect of the row to which the image corresponds.

Answer 2

Have you tried using the initWithContentsOfURL: method?

Answer 3

My solution is to use Grand Central Dispatch (GCD) for this purpose, you could save the image to disc too in the line after you got it from the server.

- (NSView *)tableView:(NSTableView *)_tableView viewForTableColumn:(NSTableColumn *)tableColumn row:(NSInteger)row
{
    SomeItem *item = [self.items objectAtIndex:row];
    NSTableCellView *cell = [_tableView makeViewWithIdentifier:tableColumn.identifier owner:self];
    if (item.artworkUrl)
    {
        cell.imageView.image = nil;
        dispatch_async(dispatch_queue_create("getAsynchronIconsGDQueue", NULL), 
        ^{
            NSURL *url = [NSURL URLWithString:item.artworkUrl];
            NSImage *image = [[NSImage alloc] initWithContentsOfURL:url];
            cell.imageView.image = image;        
        });
    }
    else
    {
        cell.imageView.image = nil;    
    }
    return cell;
}

(I am using Automatic Reference Counting (ARC) therefore there are no retain and release.)