Correct approach to an Observable Factory

[mikeymike9000]

For a view that reacts to a variable in a factory, is using a computed variable in the view model the best approach like so?:

extension Container { var myRepo: Factory<MyRepo> { self { MyRepo() }.singleton }}

@Observable final class MyRepo {
  var hash = 0
  ...
}

@Observable final class MyViewModel {
  static let shared = MyViewModel()
  @ObservationIgnored @Injected(\.myRepo) var myRepo
  var hash: Int { myRepo.hash }
  ...
}

struct MyView: View {
  @Bindable private var vm = MyViewModel.shared
  var body: some View {
    Text("hash", vm.hash)
  }
}

Also, is @InjectedObservable only for use directly in a view like so?:

struct MyView: View {
  @Bindable private var vm = MyViewModel.shared
  @InjectedObservable(\.myRepo) var myRepo
  var body: some View {
    Text("hash", myRepo.hash)
  }
}

Thanks for any suggestions! Mike

[hmlongco]

Would probably roll this way...

extension Container {
    var myRepo: Factory<MyRepo> {
        self { MyRepo() }.singleton
    }
    @MainActor
    var myViewModel: Factory<MyViewModel> {
        self { @MainActor in MyViewModel(container: self ) }
    }
}

@Observable
final class MyRepo {
    var hash = 0
    func increment() {
        hash += 1
    }
}

@MainActor
@Observable
final class MyViewModel {
    let myRepo: MyRepo
    init(container: Container) {
        self.myRepo = container.myRepo()
    }
}

struct MyView: View {
    @InjectedObservable(\.myViewModel) var vm: MyViewModel
    var body: some View {
        VStack {
            Text("hash \(vm.myRepo.hash)")
            Button("increment") {
                vm.myRepo.increment()
            }
        }
    }
}

#Preview {
    MyView()
}

Doing var hash: Int { myRepo.hash } won't work as computed values aren't observable.

[hmlongco]

And yes, InjectedObservable is for views only.

[mikeymike9000]

Nice! I can see how this is a better approach.. wow, even @Bindable is sugarcoatable

Note that var hash: Int { myRepo.hash } is reactive, as Swift 6 handles computed property bridging from a nested observable. But your approach of directly observing myRepo.hash avoids recreating individual observed properties.

Thanks Michael.. this injection stuff is pretty cool.

[mikeymike9000]

A follow up question.. instead of passing view models (that are factories) to children .fullScreenCover(isPresented: $isChildViewPresented) { MyChildView(vm: myViewModel) }

struct MyChildView: View {
  @Bindable var vm: MyViewModel
  ...
}

...is there any downside to always just inject them? .fullScreenCover(isPresented: $isChildViewPresented) { MyChildView() }

struct MyChildView: View {
  @InjectedObservable(\.myViewModel) var vm: MyViewModel
  ...
}