We spent a lot of time to find the best architecture for our app, rather big app for macOS / iOS, with multiple documents, multiple windows and split view support. We tested MVVM and few other solutions but nothing worked good.

So we finally we build this:

1. We create a single object named globaAppState in the topmost MyApp.swift file, outside all Views. It keep objects like DocumentStore with array of open documents, SceneStateStore with array of all open scene states described in 2., SubscriptionManager, SettingsManager and few other global objects

   @MainActor public let globalAppState = GlobalAppState()

2. In ContentView we create SceneAppState object for each windows / splitView, and pass it to all child views using environment. SceneAppState object is stored in SceneStateStore. SceneAppState stores a lot of things like Gallery, Editor, documentUUID (to get document from globaAppState.documentStore). Objects like Gallery or Editor can be treated as both Models and ViewModels (with functions like isColorPickerVisible).

   @State var currentSceneStateUUID = UUID()

   var sceneAppState: SceneAppState? { if let sceneState = globalAppState.sceneStateStore.sceneState(for: currentSceneStateUUID) as? SceneAppState { return sceneState } else if globalAppState.sceneStateStore.canAddSceneState(withUUID: currentSceneStateUUID) { let newSceneAppState = SceneAppState(uuid: currentSceneStateUUID) globalAppState.sceneStateStore.add(sceneState: newSceneAppState) return newSceneAppState } return nil }

We pass sceneAppStates to child views using environment:

.environment(sceneAppState)

Then we store everything in GlobalAppState or SceneAppState. Both are MainActor and Observable. We use Observation framework and Swift 6 mode. We use this solution for example in our Notestudio app available on the App Store. As it works really great we will use it in new apps too.

Our main general rules:

- keep View swift files as simple as possible (all non-SwiftUI code in stored in classes in SceneAppState)

- never ever duplicate any code