How to fire a publisher after async update in SwiftUI?

Problem

When my model housed inside a store class is updated on the main thread asynchronously, a SwiftUI view does not automatically render the slice of the model provisioned by the ViewModel.

Assumed Solution

A custom publisher / promise is needed to link the View/ViewModel/Factory/Store together, as a reference doesn't fire updates on asynchronous updates.

Block

How do I write that? I've tried adding a promise to the Store class, but Xcode warns the Result of call to sink(receiveValue:) is unused. I clearly don't understand promises / publishers and most tutorials use URLSession and its dataTaskPublisher (not my case).

I tried the example in this Apple Dev Forums thread on the factory and store classes, but no dice. I clearly don't understand it. In this answer, @Asperi suggested the View listen to a publisher and update an @State variable, but since my model is private I lack a target for that approach.

Abbreviated Code

• A factory instantiates a ContactStore class with dependencies; a reference is passed to ViewModels.
• The VMs gate access to the private store with computed variables. The view calls functions in the ViewModel that modify state, which works well if synchronous.

Factory.swift

import SwiftUI
import Combine

class MainFactory {

    init() {
        ...
        self.contactStore = ContactStore()
    }

    private var preferences: Preferences
    private var contactStore: ContactStore

 ...

    func makeOnboardingVM() -> OnboardingVM {
        OnboardingVM(preferences: preferences, contactStore: contactStore)
    }

}

ContactStore.swift

final class ContactStore {

    private(set) var authorizationStatus: CNAuthorizationStatus = .notDetermined
    private(set) var contacts: [Contact] = [Contact]()
    private(set) var errors: [Error] = [Error]()

    private lazy var initialImporter = CNContactImporterForiOS14(converter: CNContactConverterForiOS14(),
                                                                 predictor: UnidentifiedSelfContactFavoritesPredictor())
}

// MARK: - IMPORT

extension ContactStore {
    /// Full import during app onboarding. Work conducted on background thread.
    func requestAccessAndImportPhoneContacts(completion: @escaping (Bool) -> Void) {
        CNContactStore().requestAccess(for: .contacts) { [weak self] (didAllow, possibleError) in
            guard didAllow else {
                DispatchQueue.main.async { completion(didAllow) }
                return
            }
            DispatchQueue.main.async { completion(didAllow) }
            self?.importContacts()
        }
    }

    private func importContacts() {
        initialImporter.importAllContactsOnUserInitiatedThread { [weak self] importResult in
            DispatchQueue.main.async {
               switch importResult {
               case .success(let importedContacts):
                
                   self?.contacts = importedContacts
               case .failure(let error):
                   self?.errors.append(error)
               }
            }
        }
    }
}

OnboardingViewModel.swift

import SwiftUI
import Contacts

class OnboardingVM: ObservableObject {

    init(preferences: Preferences, contactStore: ContactStore) {
        self.preferences = preferences
        self.contactStore = contactStore
    }

    @Published private var preferences: Preferences
    @Published private var contactStore: ContactStore

    var contactsAllImported: [Contact] { contactStore.contacts }

    func processAddressBookAndGoToNextScreen() {
        contactStore.requestAccessAndImportContacts() { didAllow in
            DispatchQueue.main.async {
                if didAllow {
                    self.go(to: .relevantNewScreen)
                else { self.go(to: .relevantOtherScreen) }
            }
        }
    }

    ...
}
       

View.swift

struct SelectEasiestToCall: View {
    @EnvironmentObject var onboarding: OnboardingVM

    var body: some View {
        VStack {
            ForEach(onboarding.allContactsImported) { contact in 
                SomeView(for: contact)
            }
        }