Tree-Based Push onto NavigationStack using TCA

TreeBasedPush.swift

import SwiftUI

@main
struct TreeBasedPushApp: App {
    var body: some Scene {
        WindowGroup {
          TreeBasedPush_V()
        }
    }
}

import ComposableArchitecture

@Reducer struct TreeBasedPush_R {
  @Reducer enum Destination {
    case child1(Child1_R)
    case child2(Child2_R)
  }
  
  @ObservableState struct State {
    @Presents var destination: Destination.State?
  }
  enum Action {
    case destination(PresentationAction<Destination.Action>)
    case present(Destination.State)
  }
  
  var body: some ReducerOf<Self> {
    Reduce { state, action in
      switch action {
        case .destination: return .none
        case let .present(destState):
          state.destination = destState
          return .none
      }
    }
    .ifLet(\.$destination, action: \.destination)
  }
}

struct TreeBasedPush_V: View {
  @Bindable var store: StoreOf<TreeBasedPush_R> = .init(
    initialState: .init(),
    reducer: { TreeBasedPush_R()._printChanges() }
  )
  
  var body: some View {
    NavigationStack {
      List {
        Button("Child 1") { store.send(.present(.child1(.init())))}
        Button("Child 2") { store.send(.present(.child2(.init())))}
      }
      .navigationTitle("root")
      .navigationDestination(
        item: $store.scope(state: \.destination?.child1, action: \.destination.child1)
      ) { store in
        Child1_V(store: store)
      }
      .navigationDestination(
        item: $store.scope(state: \.destination?.child2, action: \.destination.child2)
      ) { store in
        Child2_V(store: store)
      }
    }
  }
}

@Reducer struct Child1_R {
  @Reducer enum Destination {
    case child1(Child1_R)
    case child2(Child2_R)
  }
  
  @ObservableState struct State {
    @Presents var destination: Destination.State?
  }
  enum Action {
    case destination(PresentationAction<Destination.Action>)
    case present(Destination.State)
  }
  
  var body: some ReducerOf<Self> {
    Reduce { state, action in
      switch action {
        case .destination: return .none
        case let .present(destState):
          state.destination = destState
          return .none
      }
    }
    .ifLet(\.$destination, action: \.destination)
  }
}

struct Child1_V: View {
  @Bindable var store: StoreOf<Child1_R> = .init(
    initialState: .init(),
    reducer: { Child1_R() }
  )
  var body: some View {
    List {
      Button("Child 1") { store.send(.present(.child1(.init())))}
      Button("Child 2") { store.send(.present(.child2(.init())))}
    }
    .navigationTitle("Child 1")
    .navigationDestination(
      item: $store.scope(state: \.destination?.child1, action: \.destination.child1)
    ) { store in
      Child1_V(store: store)
    }
    .navigationDestination(
      item: $store.scope(state: \.destination?.child2, action: \.destination.child2)
    ) { store in
      Child2_V(store: store)
    }
  }
}

@Reducer struct Child2_R {
  @Reducer enum Destination {
    case child1(Child1_R)
    case child2(Child2_R)
  }
  
  @ObservableState struct State {
    @Presents var destination: Destination.State?
  }
  enum Action {
    case destination(PresentationAction<Destination.Action>)
    case present(Destination.State)
  }
  
  var body: some ReducerOf<Self> {
    Reduce { state, action in
      switch action {
        case .destination: return .none
        case let .present(destState):
          state.destination = destState
          return .none
      }
    }
    .ifLet(\.$destination, action: \.destination)
  }
}

struct Child2_V: View {
  @Bindable var store: StoreOf<Child2_R> = .init(
    initialState: .init(),
    reducer: { Child2_R() }
  )
  var body: some View {
    List {
      Button("Child 1") { store.send(.present(.child1(.init())))}
      Button("Child 2") { store.send(.present(.child2(.init())))}
    }
    .navigationTitle("Child 2")
    .navigationDestination(
      item: $store.scope(state: \.destination?.child1, action: \.destination.child1)
    ) { store in
      Child1_V(store: store)
    }
    .navigationDestination(
      item: $store.scope(state: \.destination?.child2, action: \.destination.child2)
    ) { store in
      Child2_V(store: store)
    }
  }
}