chriswebb09

let imageCache = NSCache<NSString, UIImage>()

chriswebb09

func downloadImage(url: URL, completion: @escaping (UIImage?) -> Void) 

chriswebb09

  if let cachedImage = imageCache.object(forKey: url.absoluteString as NSString) {
            completion(cachedImage, nil)
  }

chriswebb09

static func downloadImage(url: URL, completion: @escaping (_ image: UIImage?, _ error: Error? ) -> Void) {
        if let cachedImage = imageCache.object(forKey: url.absoluteString as NSString) {
            completion(cachedImage, nil)
        } else {
            MTAPIClient.downloadData(url: url) { data, response, error in
                if let error = error {
                    completion(nil, error)
                    
                } else if let data = data, let image = UIImage(data: data) {
                    imageCache.setObject(image, forKey: url.absoluteString as NSString)

chriswebb09

let url = URL(string: "http://www.google.com")

chriswebb09

var defaultSession = URLSession(configuration: .default)

chriswebb09

@IBOutlet weak var progressView: UIProgressView!
@IBOutlet weak var downloadProgressLabel: UILabel!

chriswebb09

final class iTunesAPIClient: NSObject {
    // Network stuff
}

chriswebb09

extension iTunesAPIClient: URLSessionDelegate {
    internal func urlSessionDidFinishEvents(forBackgroundURLSession session: URLSession) {
         // Calls background session completion in AppDelegate
    }
    
    internal func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didWriteData bytesWritten: Int64, totalBytesWritten: Int64,totalBytesExpectedToWrite: Int64) {
        // Gives you the URLSessionDownloadTask that is being executed
        // along with the total file length - totalBytesExpectedToWrite
        // and the current amount of data that has received up to this point - totalBytesWritten
   }

chriswebb09

func application(_ application: UIApplication, handleEventsForBackgroundURLSession identifier: String, completionHandler: @escaping () -> Void) {
    // Background completion called here.
}