Image background service

NSData * imageData = [[NSData alloc] initWithContentsOfURL: [NSURL URLWithString: @"image url"]];

    cell.image = [UIImage imageWithData: imageData];

change to

dispatch_async(dispatch_get_global_queue(0,0), ^{

        NSData * data = [[NSData alloc] initWithContentsOfURL: [NSURL URLWithString: @"image url"]];

        if ( data == nil )

            return;

        dispatch_async(dispatch_get_main_queue(), ^{

            // WARNING: is the cell still using the same data by this point??

            cell.image = [UIImage imageWithData: data];

        });

    });