When marking the ViewController and the function with @MainActor, the assertion to check that the UI is updated on main thread fails. How do I guarantee that a function is run on Main Thread when using @MainActor? Example code: import UIKit @MainActor class ViewController: UIViewController {     let updateObject = UpdateObject()     override func viewDidLoad() {         super.viewDidLoad()                  updateObject.fetchSomeData { [weak self] _ in             self?.updateSomeUI()         }     }     @MainActor     func updateSomeUI() {         assert(Thread.isMainThread) // Assertion failed!     } } class UpdateObject {     func fetchSomeData(completion: @escaping (_ success: Bool) -> Void) {         DispatchQueue.global().async {             completion(true)         }     } } Even changing DispatchQueue.global().async to Task.detached does not work. Tested with Xcode 13.2.1 and Xcode 13.3 RC

I have enabled runtime concurrency warnings to check for future problems concerning concurrency: Build Setting / Other Swift Flags: -Xfrontend -warn-concurrency -Xfrontend -enable-actor-data-race-checks When trying to call the async form of PHPhotoLibrary.shared().performChanges{} I get the following runtime warning: warning: data race detected: @MainActor function at ... was not called on the main thread in the line containing performChanges. My sample code inside a default Xcode multi platform app template is as follows: import SwiftUI import Photos @MainActor class FotoChanger{     func addFotos() async throws{         await PHPhotoLibrary.requestAuthorization(for: .addOnly)         try! await PHPhotoLibrary.shared().performChanges{             let data = NSDataAsset(name: "Swift")!.data             let creationRequest = PHAssetCreationRequest.forAsset()             creationRequest.addResource(with: .photo, data: data, options: PHAssetResourceCreationOptions())         }     } } struct ContentView: View {     var body: some View {         ProgressView()             .task{                 try! await FotoChanger().addFotos()             }     } } You would have to have a Swift data asset inside the asset catalog to run the above code, but the error can even be recreated if the data is invalid. But what am I doing wrong? I have not found a way to run perform changes, the block or whatever causes the error on the main thread. PS: This is only test code to show the problem, don't mind the forced unwraps.

How does one add Codable conformance to a class that needs to be isolated to the MainActor? For example, the following code gives compiler errors: @MainActor final class MyClass: Codable { var value: Int enum CodingKeys: String, CodingKey { case value } init(from decoder: Decoder) throws { // <-- Compiler error: Initializer 'init(from:)' isolated to global actor 'MainActor' can not satisfy corresponding requirement from protocol 'Decodable' let data = try decoder.container(keyedBy: CodingKeys.self) self.value = try data.decode(Int.self, forKey: .value) } func encode(to encoder: Encoder) throws { // <-- Compiler error: Instance method 'encode(to:)' isolated to global actor 'MainActor' can not satisfy corresponding requirement from protocol 'Encodable' var container = encoder.container(keyedBy: CodingKeys.self) try container.encode(value, forKey: .value) } } I'm definitely struggling to get my head around actors and @MainActor at the moment!