akka/akka-core

Compose matchState methods in AbstractFSM

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#17,718 opened on Jun 15, 2015

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1 - triagedhelp wantedt:core

Description

In scala version I can do this:

    onTransition {
      case _ -> State.Pausing => log.debug("Transitioning into pausing state")
      case _ -> State.Running => log.debug("Transitioning into running state")
    }

but in Java version using matchState method I can only one state transition

onTransition(
        matchState(GameEngineState.Running, GameEngineState.Pausing,
              () -> log().debug("Transitioning into pausing state")));

We would need a way to compose matchState methods.

Contributor guide

Tech stack
scalajava
Domain
backend
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
Java 8+Akka FSM knowledge
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30
Research direction
The issue requests a method to compose multiple matchState transitions in Akka's Java API. Currently, only one matchState can be used per onTransition block. The solution could involve overloading matchState to accept multiple arguments or returning a composite object. Refer to the Scala API's onTransition with pattern matching for inspiration. Check the AbstractFSM source in akka actor/src/main/java/akka/actor/AbstractFSM.java for the current implementation.