Loading image from server in collection view - swift

Question

I have tried so many ways to load image from server in collection view, but the lag is still there when scrolling!
this is my ImageProvider class:
let imageCache = NSCache<AnyObject, AnyObject>()
class ImageProvider: UIImageView {
var imageUrl: String?
func loadImage(from urlString: String) {
self.imageUrl = urlString
let url = URL(string: urlString)!
image = nil
if let imageFromCache = imageCache.object(forKey: urlString as AnyObject) as? UIImage {
self.image = imageFromCache
return
}
URLSession.shared.dataTask(with: url) { (data, request, error) in
if error != nil {
print(error!)
return
}
DispatchQueue.main.async {
let imageToCache = UIImage(data: data!)
if self.imageUrl == urlString {
self.image = imageToCache
}
imageCache.setObject(imageToCache!, forKey: urlString as AnyObject)
}
}.resume()
}
}
setting up data:
func setupCVData(cell: TrackCell, item: Audio) {
cell.title.text = item.name
cell.url = URL(string: item.url!)!
if let url = cell.url {
var imageLink = String()
(_, _, imageLink) = fetcher.getData(from: url)
cell.imageUrl = imageLink
cell.updateImageView()
}
}
and updateImageView function:
func updateImageView() {
self.artwork.loadImage(from: imageUrl)
}
I've tried calling setupCVData in collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) and collectionView(_ collectionView: UICollectionView, willDisplay cell: UICollectionViewCell, forItemAt indexPath: IndexPath)
I also used SDWebImage with no luck!
So what am I doing wrong here? I can't seem to figure out the problem.

Answer 1

As far as I know, you don't have to create the UIImage object on the main thread. I usually create UIImages in background threads without any problems. UI elements should only be modified on the main thread, however. So when you set the UIImageView's image property, make sure that's done on the main thread.
let imageToCache = UIImage(data: data!)
imageCache.setObject(imageToCache!, forKey: urlString as AnyObject)
DispatchQueue.main.async {
if self.imageUrl == urlString {
self.image = imageToCache
}
}