Can you share an example of a technical improvement made to a project and describe its implementation?

In one of my iOS projects, I improved image loading performance in a list (UITableView) by implementing caching and asynchronous loading.

Implementation:

• Used NSCache to store already loaded images to avoid re-downloading them from the network.
• In the cellForRowAt method, checked if the image was in cache — if yes, displayed it immediately.
• If the image was not in cache, initiated asynchronous loading via URLSession, and after loading, saved the image to cache and updated the cell.

Example code:

let imageCache = NSCache<NSString, UIImage>()

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath)
    let urlString = imageURLs[indexPath.row]

    if let cachedImage = imageCache.object(forKey: urlString as NSString) {
        cell.imageView?.image = cachedImage
    } else {
        cell.imageView?.image = nil
        DispatchQueue.global().async {
            if let url = URL(string: urlString),
               let data = try? Data(contentsOf: url),
               let image = UIImage(data: data) {
                self.imageCache.setObject(image, forKey: urlString as NSString)
                DispatchQueue.main.async {
                    if let updateCell = tableView.cellForRow(at: indexPath) {
                        updateCell.imageView?.image = image
                        updateCell.setNeedsLayout()
                    }
                }
            }
        }
    }
    return cell
}

This significantly reduced network load and improved scrolling smoothness.