Question

I need implement some kind of lazy loading in my UITableView.

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    //... some initializations here

    //this is a function that pulls my cell data using helper class
    NSData *cellData=[MyDataClass dataForCellAtIndexPath:indexpath.row];

    //... here I populate pulled data to cell

    return cell;
}

Everything works great, but table view scrolls not smoothly, because dataForCellAtIndexPath method is slow. So I need to implement lazy populating data into cells by calling this method. The result I expect is that table view will scroll smoothly but cell’s content will populate a bit after the cell is drawn. Help me please, How can it be done?

Answer 1

Yes, you could look at pushing your data collection onto a background thread. The first thing to try is the simplest option to see if it improves anything:

[MyDataClass performSelectorInBackground:@selector(dataForCellAtIndexPath:) withObject:indexpath.row];

This post mentions some of the other, more complex, customisable options like Grand Central Dispatch and NSThread.