Is there a way to get notified about changes to the Actor-System?

[FloNeu]

I use xstate in angular and have a semi complex system driven by a single root actor - which orchestrates some child actors.

I use Angulars Dependency Injection to share this actor as a service - put also pick some of the nested actors to share as their own service to drive parts of the UI.

Think an Authentification-Actor used to display an Login/Logout Button depending on the users authentification status.

Currently i check on every snapshot change of the ROOT system if the desired CHILD is available and if yes push it into the service.

It's not really a problem and seems to work fine - but of course it's not the most efficient way - as most of the time these Actors are longer lived, but still i have to check if one is added/removed on every state-change.

I could imagine it to be useful being able to subscribe to actor-system changes only - but haven't found a better way to detect it.

[davidkpiano]

What you're currently doing is fine. There isn't currently a dedicated "actor system changed" or "children changed" subscription API. The closest thing is system-level inspection via actor.system.inspect(...), but that's low-level and not really meant as a higher-level child lifecycle subscription. If the child actor is long-lived and has a stable role, giving it a systemId and looking it up with actor.system.get(...) can make access cleaner, but it doesn’t replace reacting to availability changes over time.