1

I use following function func request(imageURL:completion) to download images for tableViewCells. As multiple table view cells calls this function simultaneously, how should I make sure downloaded image in URLSession corresponds to which request imageURL?

In my project, when I use resp.url under URLSession completion block, it has different address of image storage location. So I cannot use that to validate with requested imageURL.

Is there another way so I can store these image in dictionary/cache for correct request imageURL?

class ImageDownloader {
  static let shared = ImageDownloader()
  private init() { }

  var dict = [URL: UIImage]()
   func request(imageURL: URL, completion: @escaping (Result<Data, ImageFetchError>) -> Void) {

       let dataTask = URLSession.shared.dataTask(with: imageURL) { data, resp, error in
            // Response received after random seconds
  
            /*
               requestURL = https://picsum.photos/200/300
               resp.url = "https://i.picsum.photos/id/621/200/300.jpg?hmac=GgxwZqdPsVQwlM2QhfHoLU8gZ7uo_PP6oD4KmIq-ino" 
            */
           serverUrl[imageURL] = UIImage(data: data!)
      }.resume() 
   }
}

// This would be repeated in cellForItemAtIndexPath method.
class CustomCell: UICollectionViewCell {
 func downloadImage() {
   let url = URL(string: model.url) // model.url = "https://picsum.photos/200/300"
   ImageDownloader.shared.request(URL(string: url)!) { result in
   }
 }
}
2

it has different address of image storage location

???

The imageURL (bold) passed to dataTask and used inside closure is the same variable:

URLSession.shared.dataTask(with: imageURL) { data, resp, error in
serverUrl[imageURL] = ...
}

In most cases it will also be equal to resp.url

3

@vishdeshmukh can you provide some example of some image url's being retrieved, and how the ImageDownloader class is used in your code?