Fixes the xcode build and adds stubs for missing classes.

iOS/MonsterPreview/PreviewViewController.swift

@@ -3,41 +3,60 @@
 //  MonsterPreview
 //
 //  Created by Tom Hicks on 4/7/21.
+//  Last modified by Tom Hicks on 9/23/26.
 //
 
 import UIKit
 import QuickLook
 import SwiftUI
 
-class PreviewViewController: UIViewController, QLPreviewingController {
-        
-    func preparePreviewOfFile(at url: URL, completionHandler handler: @escaping (Error?) -> Void) {
-        
-        let document = MonsterDocument(fileURL: url)
-        document.open(completionHandler: {[weak self](_) in
-                        self?.presentMonsterViewController(for: document)
-                        handler(nil)
-        })
-    }
+@MainActor
+final class PreviewViewController: UIViewController, @preconcurrency QLPreviewingController {
     
-    func presentMonsterViewController(for document: MonsterDocument) {
-        let monsterViewModel = MonsterImportHelper.import5ESBMonster(document.monsterDTO ?? MonsterDTO())
-        let monsterViewController = UIHostingController(rootView: MonsterDetailView(viewModel: monsterViewModel))
-        monsterViewController.loadViewIfNeeded()
-        monsterViewController.view.layoutIfNeeded()
-        addChild(monsterViewController)
-        view.addSubview(monsterViewController.view)
-        monsterViewController.didMove(toParent: self)
-        
-        if let monsterView = monsterViewController.view {
-            monsterView.translatesAutoresizingMaskIntoConstraints = false
-            NSLayoutConstraint.activate([
-                monsterView.leftAnchor.constraint(equalTo: view.leftAnchor),
-                monsterView.rightAnchor.constraint(equalTo: view.rightAnchor),
-                monsterView.topAnchor.constraint(equalTo: view.topAnchor),
-                monsterView.bottomAnchor.constraint(equalTo: view.bottomAnchor),
-            ])
+    // MARK: - QLPreviewingController
+    
+    func preparePreviewOfFile(at url: URL, completionHandler handler: @escaping (Error?) -> Void) {
+        Task { @MainActor in
+            let document = MonsterDocument(fileURL: url)
+            
+            // Asynchronously open the document on the MainActor
+            let isOpen = await document.open()
+            
+            guard isOpen else {
+                handler(CocoaError(.fileReadCorruptFile))
+                return
+            }
+            
+            // Extract the model and display
+            let dto = document.monsterDTO ?? MonsterDTO()
+            self.presentMonsterViewController(for: dto)
+            
+            // Notify QuickLook that preview preparation succeeded
+            handler(nil)
         }
     }
-
+    
+    // MARK: - Private Presentation
+    
+    private func presentMonsterViewController(for dto: MonsterDTO) {
+        let monsterViewModel = MonsterImportHelper.import5ESBMonster(dto)
+        let hostingController = UIHostingController(rootView: MonsterDetailView(viewModel: monsterViewModel))
+        
+        // Add as child view controller
+        addChild(hostingController)
+        view.addSubview(hostingController.view)
+        
+        // Configure layout constraints
+        let subview = hostingController.view!
+        subview.translatesAutoresizingMaskIntoConstraints = false
+        
+        NSLayoutConstraint.activate([
+            subview.leadingAnchor.constraint(equalTo: view.leadingAnchor),
+            subview.trailingAnchor.constraint(equalTo: view.trailingAnchor),
+            subview.topAnchor.constraint(equalTo: view.topAnchor),
+            subview.bottomAnchor.constraint(equalTo: view.bottomAnchor)
+        ])
+        
+        hostingController.didMove(toParent: self)
+    }
 }