AsyncImageDownloadOperation.swift

import UIKit

class AsyncImageDownloadOperation: AsyncOperation {

    var downloadedImage: UIImage?

    override func main() {
        let defaultSession = URLSession(configuration: .default)
        guard let imgUrl = URL(string: "https://unsplash.com/photos/M9O6GRrEEDY/download?force=true") else { return }
        let dataTask = defaultSession.dataTask(with: imgUrl) { (data, response, error) in
            if let error = error {
                print("Image download encountered an error: \(error.localizedDescription)")
            } else if let data = data, let response = response as? HTTPURLResponse,
                response.statusCode == 200 {
                if self.isCancelled {
                    self.state = .finished
                    return
                }
                let image = UIImage(data: data)
                self.downloadedImage = image
                self.state = .finished
            }
        }
        dataTask.resume()
    }
}