How do I scope to an enum and then do .ifCaseLet?

[oliverfoggin]

I'm working with the protocol beta branch.

I had a feature like this:

public enum State: Equatable {
  case login(LoginFeature.State)
  case mainApp(MainAppFeature.State)
  ...
}

In my reducer I was able to switch between states and then use .ifCaseLet to scope to the various cases...

public var body: some ReducerProtocol<State, Action> {
  Reduce { state, action in
    case .something:
      state = .login(.init())
      return .none
  }
  .ifCaseLet(/State.login, action: /Action.login) {
    LoginFeature()
  }
  .ifCaseLet...
}

But now I wanted to change it so that the State is now a struct that contains this enum...

public struct State: Equatable {
  enum AppMode: Equatable {
    case login(LoginFeature.State)
    case mainApp(MainAppFeature.State)
    ...
  }

  var appMode: AppMode
}

But I'm struggling with how to update the reducer to work with this.

I tried creating a Scope reducer and then doing .ifCaseLet on that but I think I got that wrong. 😅

The compiler complains it cannot type-check the reducer in a reasonable time.

In the old way I think I would have done a scope and then case on the Login reducer but now I'm not so sure with this.

Any guidance would be appreciated. Thanks

[mbrandonw]

This is unfortunately a blind spot in the library right now. We don't provide an ergonomic tool to first scope to an enum field and then further scope to a case. There is a workaround though, which you can use until we come up with a better tool.

[mbrandonw]

And you should also read Stephen's follow comment (and link) in that thread.

[oliverfoggin]

Thanks, I'll have a read now.

[oliverfoggin]

Oh man! I was so close. I just didn't get the order of Scope and EmptyReducer and ifCaseLet correct. 😄