Optional Presentation functionality on the navigation-beta branch

[emlynmac]

I’m working through updating my app to TCA ReducerProtocol and I’m looking to include the navigation components laid out with Destinations.
I’ve got my project hooked up to TCA navigation-beta branch and have a basic sheet implementation almost working.

I’m using this as a reference for the implementation:
https://github.com/pointfreeco/episode-code-samples/blob/5c17384710ae8ef9bc3457a7d1d9fc7982281ea8/0229-composable-navigation-pt8/Inventory/Inventory/Inventory.swift#L319

The main issue I have is that the .sheet view modifier in the episode does not seem to be in the navigation-beta branch:
https://github.com/pointfreeco/episode-code-samples/blob/5c17384710ae8ef9bc3457a7d1d9fc7982281ea8/0229-composable-navigation-pt8/Inventory/Inventory/Navigation.swift#L147

It looks to me like the view modifier should have optional presentation state in this file:

swift-composable-architecture/Sources/ComposableArchitecture/SwiftUI/Sheet.swift

Line 20 in 5fbce50

store: Store<PresentationState<State>, PresentationAction<Action>>,

Am I missing something or should this be optional?

If I use the functions from the episode, I'm good to go:

extension View {
  func sheet<DestinationState, DestinationAction, ChildState: Identifiable, ChildAction>(
    store: Store<DestinationState?, PresentationAction<DestinationAction>>,
    state toChildState: @escaping (DestinationState) -> ChildState?,
    action fromChildAction: @escaping (ChildAction) -> DestinationAction,
    @ViewBuilder child: @escaping (Store<ChildState, ChildAction>) -> some View
  ) -> some View {
    self.sheet(
      store: store.scope(
        state: { $0.flatMap(toChildState) },
        action: {
          switch $0 {
          case .dismiss:
            return .dismiss
          case let .presented(action):
            return .presented(fromChildAction(action))
          }
        }
      ),
      child: child
    )
  }
  
  func sheet<ChildState: Identifiable, ChildAction>(
      store: Store<ChildState?, PresentationAction<ChildAction>>,
      @ViewBuilder child: @escaping (Store<ChildState, ChildAction>) -> some View
    ) -> some View {
      WithViewStore(store, observe: { $0?.id }) { viewStore in
        self.sheet(
          item: Binding(
            get: { viewStore.state.map { Identified($0, id: \.self) } },
            set: { newState in
              if viewStore.state != nil {
                viewStore.send(.dismiss)
              }
            }
          )
        ) { _ in
          IfLetStore(
            store.scope(
              state: returningLastNonNilValue { $0 },
              action: PresentationAction.presented
            )
          ) { store in
            child(store)
          }
        }
      }
    }
}

func returningLastNonNilValue<A, B>(
  _ f: @escaping (A) -> B?
) -> (A) -> B? {
  var lastValue: B?
  return { a in
    lastValue = f(a) ?? lastValue
    return lastValue
  }
}

[stephencelis]

@emlynmac Are you caught up on episodes? The sample you link to is from 229, which is before the PresentationState property wrapper is introduced. This property wrapper bakes in optionality, and is used in the navigation-beta branch.

If you share a full code sample that you're trying to get to work on navigation-beta we can try to help steer you in the right direction.

[emlynmac]

Thanks @stephencelis. I was not fully caught up...
I realized after looking at my code a little more closely, the magic I was missing.
Using: @PresentationState var destination: Destination.State? in my app state and then the issue in the SwiftUI was to add the missing $

.sheet(
  store: self.store.scope(
    state: \.$destination,                                 //// This was just \.destination previously
    action: AppRootLogic.Action.destination
  ),
...

I've now got the prerelease/1.0 branch in my project and zero deprecation warnings, and everything is happy.