SwiftUIActorSync.swift

final actor Worker: ObservableObject {
    @MainActor @Published private(set) var lastWorkDoneAt: Date?

    private var counter = 0
    
    func doWork() {
        counter += 1
        
        DispatchQueue.main.async {
            self.lastWorkDoneAt = .now
        }
    }
    
    func fetchWorkCounter() -> Int {
        return counter
    }
}

struct MyTestView: View {
    @StateObject private var worker = Worker()
    @State private var queuedWorkCount: Int = 0
    @State private var fetchedWorkCount: Int = 0

    var body: some View {
        VStack {
            Text("Queued Work Count: \(queuedWorkCount)")
            Text("Fetched Work Count: \(fetchedWorkCount)")

            Divider()

            Button {
                Task {
                    for i in 1...100 {
                        queuedWorkCount += 1
                        await worker.doWork()
                    }
                }
            } label: {
                Text("Enqueue 100 Work")
            }
        }
        .task(id: worker.lastWorkDoneAt) {
            fetchedWorkCount = await worker.fetchWorkCounter()
        }
    }
}

Would an approach more like this work, where you publish the completed work and use that directly in the view?

final actor Worker: ObservableObject {
    @MainActor @Published private(set) var publishedCount: Int?

    @Published private(set) var counter = 0

    func doWork() async {
        counter += 1

        Task { @MainActor [counter] in
            self.publishedCount = counter
        }
    }

    func fetchWorkCounter() -> Int {
        return counter
    }
}
struct MyTestView: View {
    @StateObject private var worker = Worker()
    @State private var queuedWorkCount: Int = 0
    @State private var fetchedWorkCount: Int = 0
    
    var body: some View {
        VStack {
            Text("Queued Work Count: \(queuedWorkCount)")
            Text("Fetched Work Count: \(worker.publishedCount ?? 0)")
            Divider()
            Button {
                Task {
                    for i in 1...100 {
                        queuedWorkCount += 1
                        await worker.doWork()
                    }
                }
            } label: {
                Text("Enqueue 100 Work")
            }
        }
    }
}

That's not the same as what I am going for, I think. The real Worker actor is managing a database, so I was looking for a way to generate an event that basically just means, "some data has changed, you need to re-run your query and update your UI."

So somewhere else in the app, a record may be added to the worker actor with something like: await worker.save(record) - possibly even as a background process or something triggered by a timer somewhere. After the record is actually been saved, I wanted to trigger a signal so UI elsewhere in the app can re-query their view and see the changes. Of course it's not as perfectly efficient as noting exactly what changed and only updating exactly those objects and views or whatever, but I figured this would be close enough. I think the idea would work okay except I ran into this.