mvvm - ViewModel Async Func 完成时如何从 subview 更新 EnvironmentObject

Question

在我的 SwiftUI 应用程序中，我有一个入口点，如下所示

@main
struct SomeApp: App {
    @UIApplicationDelegateAdaptor(AppDelegate.self) var appDelegate
    var body: some Scene {
        WindowGroup {
            AppContainerView()
        }
    }
}

struct AppContainerView: View {
    @StateObject var appState = AppState()
    var body: some View {
        if appState.isLoggedIn && appState.hasSeenOnboarding {
            TabContainerView()
        } else {
            LandingView().environmentObject(appState)
        }
    }
}

我可以更新 isLoggedIn像这样...

class AppState: ObservableObject {
    var cancellables: [AnyCancellable] = []
    private let userService: UserServiceProtocol
    init(userService: UserServiceProtocol = UserService()) {
        self.userService = userService
        subscribeForAuthChanges()
    }
    
    func subscribeForAuthChanges() {
        userService.authChangeSubject.sink(receiveValue: { [weak self] auth, user in
            print(auth)
            if user != nil {
                self?.isLoggedIn = true
            }
        }).store(in: &cancellables)
    }
    
    @Published var isLoggedIn = false
    @Published var hasSeenOnboarding = false
}

但是说到 hasSeenOnboarding在 LandingView 之一的 viewModel 中完成某些网络调用后，需要将此设置为 true child 的意见。我可以做这样的事情......

struct ChildView: View {
  @EnvironmentObject var appState: AppState
  @StateObject var viewModel = ChildViewModel()

  var body: some View {
    VStack {
      //...
    }.onReceive($viewModel.networkCallCompleted) { completed in
       self.appState.hasSeenOnboarding = completed
    }
  }
}

但这感觉不对……在使用 MVVM 时，这里有更好的选择来从 childView/viewModel 更改 appState 吗？或者也许是更好的方法？

Answer 1

一种可能的替代方法是通过 AppState到ChildViewModel并执行AppState直接在 View 模型中更新。

struct ParentView: View {
  @EnvironmentObject var appState: AppState

  var body: some View {
    ChildView(viewModel: ChildViewModel(appState: appState))
  }
}

struct ChildView: View {
  @EnvironmentObject var appState: AppState
  @StateObject var viewModel: ChildViewModel

  var body: some View {
    ...
  }
}

备注
你可能想看看 依赖注入(inject) 使其更清洁。这是一个可能的例子: Simple Dependency Injection using @propertyWrapper .