How to hookup Sparkle in SwiftUI

SparkleCommands.swift

//
//  SparkleCommands.swift
//  Past for iChat
//
//  Created by Helge Heß on 08.04.21.
//

import SwiftUI

#if SPARKLE && canImport(Sparkle)
  import Sparkle

  /**
   * Adds the "Check for Updates" menu if Sparkle is enabled (i.e. can be
   * imported and the `SPARKLE` compilation condition is set.
   *
   * Using it in an app:
   *
   *     @main
   *     struct PastApp: App { // https://zeezide.de/en/products/past/
   *       var body: some Scene {
   *         DocumentGroup(viewing: PastDocument.self) { file in
   *           ContentView(document: file.$document)
   *         }
   *         .commands {
   *           TextFormattingCommands()
   *           SparkleCommands() // Just drop it in here
   *         }
   *       }
   *     }
   *
   * One may want to make settings like `automaticallyChecksForUpdates` user
   * configurable in the app preferences:
   *
   *     @main
   *     struct PastApp: App { // https://zeezide.de/en/products/past/
   *
   *       @AppStorage("autoUpdate") var doAutoUpdates = true
   *
   *       var body: some Scene {
   *         DocumentGroup(viewing: PastDocument.self) { file in
   *           ContentView(document: file.$document)
   *         }
   *         .commands {
   *           TextFormattingCommands()
   *           SparkleCommands(
   *             automaticallyChecksForUpdates: doAutoUpdates
   *           )
   *         }
   *
   *         Settings {
   *           YourSettingsView(doAutoUpdates: $doAutoUpdates)
   *         }
   *       }
   *     }
   */
  struct SparkleCommands: Commands {
    
    private var automaticallyChecksForUpdates : Bool
    private var automaticallyDownloadsUpdates : Bool
    private var updateCheckInterval           : TimeInterval
    private var userAgentString               : String?
    private var httpHeaders                   : [ String : String ]?
    private var sendsSystemProfile            : Bool

    init(automaticallyChecksForUpdates : Bool    = true,
         automaticallyDownloadsUpdates : Bool    = false,
         sendsSystemProfile            : Bool    = false,
         updateCheckInterval           : TimeInterval = 24 * 60 * 60 /*daily*/,
         userAgentString               : String? = nil,
         httpHeaders                   : [ String : String ]? = nil)
    {
      self.automaticallyChecksForUpdates = automaticallyChecksForUpdates
      self.automaticallyDownloadsUpdates = automaticallyDownloadsUpdates
      self.sendsSystemProfile            = sendsSystemProfile
      self.updateCheckInterval           = updateCheckInterval
      self.userAgentString               = userAgentString
      self.httpHeaders                   = httpHeaders

      let me = self
      DispatchQueue.main.asyncAfter(deadline: .now() + .seconds(1)) {
        SparkleCommands.update(with: me)
      }
    }
    
    var body: some Commands {
      CommandGroup(after: .appInfo) {
        Button("Check for Updates …") {
          SparkleCommands.updater?.checkForUpdates()
        }
      }
    }

    fileprivate static var updater : SPUUpdater?
    
    private final class SparkleDelegate:
      NSObject, SPUUpdaterDelegate, SPUStandardUserDriverDelegate {}
    private static let delegate = SparkleDelegate()

    private static func update(with configuration: SparkleCommands) {
      func configure(updater: SPUUpdater) {
        updater.automaticallyChecksForUpdates =
          configuration.automaticallyChecksForUpdates
        updater.automaticallyDownloadsUpdates =
          configuration.automaticallyDownloadsUpdates
        updater.sendsSystemProfile  = configuration.sendsSystemProfile
        updater.updateCheckInterval = configuration.updateCheckInterval
        if let v = configuration.userAgentString { updater.userAgentString = v }
        if let v = configuration.httpHeaders     { updater.httpHeaders     = v }
      }
      
      if let updater = SparkleCommands.updater {
        configure(updater: updater)
      }
      else {
        let updateDriver = SPUStandardUserDriver(hostBundle: .main,
                                                 delegate: delegate)
        let updater = SPUUpdater(hostBundle: .main, applicationBundle: .main,
                                 userDriver: updateDriver, delegate: delegate)
        configure(updater: updater)
        SparkleCommands.updater = updater
        
        do {
          try updater.start()
          updater.checkForUpdatesInBackground()
        }
        catch {
          print("ERROR: failed to start Sparkle updater:", error)
        }
      }
    }
  }
#else // No Sparkle

  /**
   * Sparkle is inactive, this will yield no commands.
   */
  struct SparkleCommands: Commands {
    let body = EmptyCommands()
  }
#endif

SwiftUIAppUsingSparkle.swift

@main
struct PastApp: App { // https://zeezide.de/en/products/past/

  var body: some Scene {

    DocumentGroup(viewing: PastDocument.self) { file in
      ContentView(document: file.$document)
    }
    .commands {
      TextFormattingCommands()
      AboutCommands()
      SparkleCommands() // Just drop it in here
    }
  }
}