Wrong Images Loaded to TableView - swift

Question

This is my first time using NSCache for a table view. For cellForRow I call an NSCache loading an image. The image sometimes is the wrong image. What can I do to fix this? If the cache does not contain it, I replace the photo with "randomguy".
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "MyMessagesTableViewCell", for: indexPath) as! MyMessagesTableViewCell
if let cachedImage = cache.object(forKey: urlArray[indexPath.row] as NSString) as? UIImage {
cell.proPicImageView.image = cachedImage
cell.proPicImageView.layer.cornerRadius =
cell.proPicImageView.frame.size.height / 2
cell.proPicImageView.layer.masksToBounds = true
cell.proPicImageView.layer.borderWidth = 0
cell.usernameLabel.text = usernameArray[indexPath.row]
cell.messageLabel.text = messageArray[indexPath.row]
cell.messageLabel.textColor = colorArray[indexPath.row]
cell.messageLabel.font = fontArray[indexPath.row]
cell.timeLabel.text = timeArray[indexPath.row]
} else {
cell.proPicImageView.image = UIImage(named: "randomguy")
cell.proPicImageView.layer.cornerRadius =
cell.proPicImageView.frame.size.height / 2
cell.proPicImageView.layer.masksToBounds = true
cell.proPicImageView.layer.borderWidth = 0
cell.usernameLabel.text = usernameArray[indexPath.row]
cell.messageLabel.text = messageArray[indexPath.row]
cell.messageLabel.textColor = colorArray[indexPath.row]
cell.messageLabel.font = fontArray[indexPath.row]
cell.timeLabel.text = timeArray[indexPath.row]
}
return cell
}
In view Did Load:
let cache = NSCache()
func photoQuery () {
for username in self.usernameArray {
let photoQuery = PFQuery(className: "UserPhoto")
photoQuery.whereKey("username", equalTo: username)
photoQuery.findObjectsInBackground(block: { (objects:
[PFObject]?,error: Error?) in
if let objects = objects {
for object in objects {
if error == nil {
let userImageFile = object["photo"] as? PFFileObject
let urlString = userImageFile?.url as! String
if let url = URL(string: urlString) {
let data = try? Data(contentsOf: url)
if let imageData = data {
self.messageImageArray.append(UIImage(data:imageData)!)
self.cache.setObject(UIImage(data:imageData)!, forKey: urlString as
NSString)
self.urlArray.append(urlString as NSString)
print(self.messageImageArray)
}
}
}
}
}
})
}
}

Answer 1

This can be one way where you can create your custom image view and have a function inside this that will take care of downloading and assigning image to the proper cell
let cache = NSCache<NSString, UIImage>()
class CustomImageView: UIImageView {
var imageURLString: String?
func startImageDownloadOperation(url: URL) {
imageURLString = url.absoluteString
if let cachedVersion = cache.object(forKey: url.absoluteString as NSString) {
self.image = cachedVersion
} else {
let task = URLSession.shared.dataTask(with: url) { (data, response, error) in
guard error == nil,
let response = response as? HTTPURLResponse,
response.statusCode == 200 else {
DispatchQueue.main.async {
self.image = UIImage(named: "default")
}
return
}
DispatchQueue.main.async {
if let data = data {
let imageToCache = UIImage(data: data)
if url.absoluteString == self.imageURLString {
self.image = imageToCache
cache.setObject(imageToCache!, forKey: url.absoluteString as NSString)
}
}
}
}
task.resume()
}
}
}