DataModelURLSessionDownloadDelegate.swift

extension DataModel: URLSessionDownloadDelegate {
  func urlSession(_ session: URLSession,
                  downloadTask: URLSessionDownloadTask,
                  didFinishDownloadingTo location: URL) {
    if let data = try? Data(contentsOf: location) {
      let image = UIImage(data: data)
      DispatchQueue.main.async {
        self.image = image
      }
    }
  }
  
  func urlSession(_ session: URLSession,
                  downloadTask: URLSessionDownloadTask,
                  didWriteData bytesWritten: Int64,
                  totalBytesWritten: Int64,
                  totalBytesExpectedToWrite: Int64) {
    if let download = activeDownload {
      download.progress = Float(totalBytesWritten)/Float(totalBytesExpectedToWrite)
    }
  }
  
  var downloadsSession : URLSession {
    get {
      let config = URLSessionConfiguration.background(withIdentifier: "background")
      let queue = OperationQueue()
      return URLSession(configuration: config, delegate: self, delegateQueue: queue)
    }
  }
}