UIImageView not loading sometimes - swift

Question

I have a function that is loading a pic of the user from URL that is using this UIImageView extension:
let imageCache = NSCache<AnyObject, AnyObject>()
extension UIImageView {
func loadImageUsingCacheWithUrlString(urlString: String) {
self.image = nil
print("here the URL of the image", urlString)
//check cache for image first
if let cachedImage = imageCache.object(forKey: urlString as AnyObject) {
self.image = cachedImage as? UIImage
return
}
// otherwise fire off a new download
let url = URL(string: urlString)
URLSession.shared.dataTask(with: url!, completionHandler: { (data, response, error) in
if error != nil {
print(error!)
return
}
DispatchQueue.main.async {
if let downloadedImage = UIImage(data: data!) {
imageCache.setObject(downloadedImage, forKey: urlString as AnyObject)
self.image = downloadedImage
}
}
}).resume()
}
}
Now, the problem I have is, that sometimes the the profile picture is loaded and sometimes not. I suppose that this happen because the function download the image asynchronously, but why once it's downloaded it doesn't appear On the profile?
I'm calling it with:
if hostPerfil != nil {
if let photo = hostPerfil?.picture {
hostPic.loadImageUsingCacheWithUrlString(urlString: photo)
}
hostName.text = hostPerfil!.firstName
}
What am I doing wrong? Can anyone help me with this, please?

Answer 1

When you get the image from your imageCache, you need to set the image of the UIImageView within the main UI thread so that it will be rendered properly. You did that when you download it, that is why it is displaying, but you have to do it as well when you are getting it from cache.
DispatchQueue.main.async {
if let cachedImage = imageCache.object(forKey: urlString as AnyObject) {
self.image = cachedImage as? UIImage
return
}
}