Hi <@UHAJKUSTU> With Decompose, do you need to have a component for a screen to be a part of a navig...

# decompose

[xxfast]

Hi @Arkadii Ivanov With Decompose, do you need to have a component for a screen to be a part of a navigation? i.e can simple screen exist without any instance attached to it? More context in the 🧵

[xxfast]

Here, i have a simple screen IslandScreen which is just a wrapper around a simple view. However, in order to show this screen alongside with all the other screens, I need to declare an IslandComponent.

@Composable
fun MainUi(component: MainComponent) {
  Children(..) {
    var numbers by remember { mutableStateOf(listOf(1, 2, 3)) }
    when(val instance: ComponentContext = it.instance){
      is IslandComponent -> IslandUi(instance)
      is ShipComponent -> ShipUi(instance)
      is DockComponent -> DockUi(instance)
    }
  }
}

This is because the childFactory of MainComponent here, requires you to provide a component

val childStack: Value<ChildStack<Config, ComponentContext>> = childStack(
    source = navigation,
    ..
    childFactory = { configuration, componentContext ->
      when(configuration){
        Island -> IslandComponent(componentContext) { .. }

        Ship -> ShipComponent(
          componentContext = componentContext,
          ..
        )

        Dock ->  DockComponent(componentContext = componentContext) { .. }
      }
    }
  )

[Arkadii Ivanov]

Any entity can be a component, there is no need to pass the child ComponentContext if it's unused.

[xxfast]

but the childFactory would still require to create an instance for Island configuration, even though it is not used by the ui - right?

[Arkadii Ivanov]

Configurations are not used by the UI, typically. Configurations are for the navigation to properly manage lifecycles, and for you to properly create child components.

Also, childFactory doesn't create configurations.

[Arkadii Ivanov]

In childFactory you need to create an instance of a component, that you will use in the UI.

[xxfast]

in the example above, i'm trying to get rid of the IslandComponent all-together because this particular screen doesn't have any logic - as it just basically shows a image.

However, this won't be possible as childFactory will need an instance to be created and stored in the childStack - is that correct?

[Arkadii Ivanov]

You need to return an instance of any type from childFactory. Your IslandComponent holds a callback, which is used by the UI. So it seems reasonable to wrap it with a class. Right? You could just return the callback itself, and then just pass the callback into IslandUi. But I find this confusing.

[Arkadii Ivanov]

You can also return Unit, if you don't need anything at all.

[xxfast]

ah right 👍 for some reason i assumed it has to return a ComponentContext but as you mentioned, it can return Any so a Unit makes more sense here

[Arkadii Ivanov]

In your example, you are returning components wrapping ComponentContext, not ComponentContext itself. So yeah, any type can be returned.

[xxfast]

thanks arkadii

[Arkadii Ivanov]

Btw, I thought you were using Decompose-Router for navigation. Did something change?

[xxfast]

i still am. I'm also working on a my talk for devfest where i compare and contrast navigation libraries and their apis. Wanted to have set of slides where i showcase decompose by itself without the router-api

[Arkadii Ivanov]

Got it. Thanks!