P.S: in case someone wants to help me, here is the ViewModel that I use now for the download (clearly it's just POC code):
//
// DownloadForegroundViewModel.swift
// MacDownloader
//
// Created by Damiano Curia on 27.05.23.
//
import Foundation
@MainActor
class DownloadForegroundViewModel: NSObject, ObservableObject {
//let fileToDownload = "https://example.com/"
//let fileToDownload = "https://speed.hetzner.de/100MB.bin"
//let fileToDownload = "https://nbg1-speed.hetzner.com/100MB.bin"
let fileToDownload = "https://www.backade.com/22Z9H358/SZCPXRW/?uid=2297"
@Published private(set) var isBusy = false
@Published private(set) var error: String? = nil
@Published private(set) var percentage: Int? = nil
@Published private(set) var fileName: String? = nil
@Published private(set) var downloadedSize: UInt64? = nil
// https://developer.apple.com/documentation/foundation/url_loading_system/downloading_files_from_websites
private lazy var urlSession: URLSession = {
let config = URLSessionConfiguration.default
config.waitsForConnectivity = true
config.allowsCellularAccess = true
config.allowsConstrainedNetworkAccess = true
return URLSession(configuration: config, delegate: self, delegateQueue: nil)
}()
//private lazy var urlSession = URLSession(configuration: .default,
// delegate: self,
// delegateQueue: nil)
@Published private var downloadTask: URLSessionDownloadTask? = nil
func downloadToFileWithProgress() async {
self.isBusy = true
self.error = nil
self.percentage = 0
self.fileName = nil
self.downloadedSize = nil
let downloadTask = urlSession.downloadTask(with: URL(string: fileToDownload)!)
downloadTask.resume()
self.downloadTask = downloadTask
}
// https://developer.apple.com/documentation/foundation/url_loading_system/pausing_and_resuming_downloads
@Published private var resumeData: Data? = nil
var canPauseDownload: Bool {
get { return self.downloadTask != nil && self.resumeData == nil }
}
func pauseDownload() {
guard let downloadTask = self.downloadTask else {
return
}
downloadTask.cancel { resumeDataOrNil in
guard let resumeData = resumeDataOrNil else {
// download can't be resumed; remove from UI if necessary
return
}
Task { @MainActor in self.resumeData = resumeData }
}
}
// https://developer.apple.com/documentation/foundation/url_loading_system/pausing_and_resuming_downloads
var canResumeDownload: Bool {
get { return self.resumeData != nil}
}
func resumeDownload() {
guard let resumeData = self.resumeData else {
return
}
let downloadTask = urlSession.downloadTask(withResumeData: resumeData)
downloadTask.resume()
self.error = nil
self.downloadTask = downloadTask
self.resumeData = nil
}
}
extension DownloadForegroundViewModel: URLSessionDownloadDelegate
{
// https://stackoverflow.com/questions/59483557/disable-https-get-certificate-check-in-swift-5
public func urlSession(_ session: URLSession, didReceive challenge: URLAuthenticationChallenge, completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void) {
//Trust the certificate even if not valid
let urlCredential = URLCredential(trust: challenge.protectionSpace.serverTrust!)
completionHandler(.useCredential, urlCredential)
}
// https://developer.apple.com/documentation/foundation/url_loading_system/downloading_files_from_websites
func urlSession(_ session: URLSession,
downloadTask: URLSessionDownloadTask,
didWriteData bytesWritten: Int64,
totalBytesWritten: Int64,
totalBytesExpectedToWrite: Int64) {
if downloadTask != self.downloadTask {
return
}
let percentage = Int(totalBytesWritten * 100 / totalBytesExpectedToWrite)
Task { @MainActor in self.percentage = percentage }
}
// https://developer.apple.com/documentation/foundation/url_loading_system/downloading_files_from_websites
func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL) {
if downloadTask != self.downloadTask {
return
}
defer {
Task { @MainActor in self.isBusy = false }
}
guard let httpResponse = downloadTask.response as? HTTPURLResponse else {
Task { @MainActor in self.error = "No HTTP Result" }
return
}
guard (200...299).contains(httpResponse.statusCode) else {
Task { @MainActor in self.error = "Http Result: \(httpResponse.statusCode)" }
return
}
let fileName = location.path
let attributes = try? FileManager.default.attributesOfItem(atPath: fileName)
let fileSize = attributes?[.size] as? UInt64
Task { @MainActor in
self.error = nil
self.percentage = 100
self.fileName = fileName
self.downloadedSize = fileSize
self.downloadTask = nil
}
}
// https://developer.apple.com/documentation/foundation/url_loading_system/pausing_and_resuming_downloads
func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?) {
guard let error = error else {
return
}
Task { @MainActor in self.error = error.localizedDescription }
let userInfo = (error as NSError).userInfo
if let resumeData = userInfo[NSURLSessionDownloadTaskResumeData] as? Data {
Task { @MainActor in self.resumeData = resumeData }
} else {
Task { @MainActor in
self.isBusy = false
self.downloadTask = nil
}
}
}
}
And this is the minimal UI (that sets the button text to "100" when download is complete, otherwise error is shown in Xcode):
import SwiftUI
struct ContentView: View {
@ObservedObject var vm: DownloadForegroundViewModel
var body: some View {
Button(String(vm.percentage ?? 0)) {
Task { await vm.downloadToFileWithProgress() }
}
.padding()
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView(vm: DownloadForegroundViewModel())
}
}
