NavigationStack(path:root:destination:) not rendering root view when scoping the store into a new one.

[danielsan22]

Description

Hi all, first of all, great work on this library!

I wanted to implement navigation within the app I'm working on to learn/practice more about TCA, I implemented a new feature RootFeature that will hold the state of the stack, and added there the initial state of my top most feature to then scope it out and have it as the root of the NavigationStack(path:root:destination) view.
But when building the main feature using the RootFeature I only get a white screen, that does loads and sends the initial .onTask action but never updates anything else, even when printing the changes on the reducer I can see that there is no change on the state and no other action is sent even tho the .onTask sends an array of data.

However, if I create a new store and pass it to the MainView inside the root parameter of the NavigationStack I do get the screen displaying and all the functionality that I expect, but I haven't found a way of comunicating to the parent RootFeature and get the actions that then will trigger the navigation I have defined on the RootFeature.

I am unsure if this is something that I should be doing or not or instead focus on having all the navigation logic directly inside the feature that will be the "true" root feature, but I like having my features a bit more isolated, thats why having the RootFeature take care of all the details of the other screens/features makes sense to me, it is also how I understood the docs since the examples use a simple NavigationLink as root (which to my app does not make sense to do that).

Checklist

• I have determined whether this bug is also reproducible in a vanilla SwiftUI project.
• If possible, I've reproduced the issue using the main branch of this package.
• This issue hasn't been addressed in an existing GitHub issue or discussion.

Expected behavior

The NavigationStack's root view can be created using a scoped version of the RootFeature's store and renders and works with all the defined actions.

Actual behavior

The NavigationStack's root view is not displayed and the console prints out no changes to the sate even when they are hard-coded as when the view loads.

Steps to reproduce

I have created a brand new project and recreated the issue there.

The Composable Architecture version information

1.9.2

Destination operating system

iOS 17

Xcode version information

15.0

Swift Compiler version information

swift-driver version: 1.82.2 Apple Swift version 5.9 (swiftlang-5.9.0.114.10 clang-1500.0.29.1)
Target: arm64-apple-macosx13.0

[mbrandonw]

Hi @danielsan22, the problem is in the body of the RootFeature:

https://github.com/danielsan22/NavStackReproduction/blob/973142a5ef7a4e7153d7fbe2a6ef97bf7d315256/NavStackReproduction/RootView.swift#L19-L31

You aren't composing the MainFeature reducer into this at all. It should be more like this:

 var body: some ReducerOf<Self> {
+    Scope(state: \.cardsSets, action: \.cardsSets) {
+      MainFeature()
+    }
     Reduce { _, action in
         switch action {
         case .path:
             return .none
         case .cardSets:
             return .none
         }
     }
     .forEach(\.path, action: \.path) {
         Path()
     }
 }

[mbrandonw]

Since this isn't an issue with the library I am going to convert it to a discussion. Please feel free to continue to discuss over there.

[danielsan22]

Ah that was it, I was under the impresion that I only needed that for the views that where going to be on the stack.
Thanks for the help!

[danielsan22]

I have a follow up question about stack based navigation:
When using stack-based navigation, how can a deeply nested feature (FeatureB) communicate with the previous feature that invoke it (FeatureA)?
The current approach is to listen to child events on the RootFeature and then push the feature to the stack, but there is no way to listen for child features inside a child feature
eg: I have the following feature stack in the StackState: RootFeature -> MainFeature -> FeatureA -> FeatureB.

What I would like to do is to get the actions of FeatureB inside FeatureA to update accordingly, which I don't know how to do because the navigation is all driven by the RootFeature.

I also tried to use a NavigationLink inside FeatureA, to have FeatureB.State as an optional state and therefore be able to listen to the actions of FeatureB, but I haven't found an overload that will allow me to push it to the RootFeature path, which I feel like can lead to some weird issues in the future.
EDIT: Digging deeper rin the Standups Series's examples I found the way to push directly from the view. So the only question would be how to listen for the updates on a more dynamic way, as for that I haven't found an example yet.

[danielsan22]

I've seen this on the Stanups series, listening to the delegate of the deeply nested feature and then using something like let detailID = state.path.ids.dropLast().last to get the previous state and perform the changes we need there, but I was wondering if there is a more dynamic way of handling this, as the solution used on the Standups App is assuming the previously pushed feature is a specific one instead of allowing whatever feature wants to push a feature and act upon its actions.

[mbrandonw]

There are just tradeoffs to using a fully statically typed navigation stack versus a dynamic one. If you want to use a statically typed one, as we do in SyncUps, then you have to do some extra work to analyze each feature in the stack and see what is going on. I can't provide any general guidance for you other than the StackAction and StackState hold all of the information you need to figure things out.