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Change Log

1.2.1 (2024-01-07)

  • Fix deadlock when using ExecutionPolicy.ORDERED.
  • Reduce allocations in rememberStateAndDispatch. Thanks to @hoc081098 for teh contribution.
  • Updated to Kotlin 1.9.22.

1.2.0 (2023-07-28)

DSL additions

  • Added new condition block that allows specifying additional condition for a state. The block supports all the same methods that inState supports.
    spec {
      inState<MyState> {
        // general onEnter/onAction/... methods
        condition({ state -> state.value == "condition" }) { 
          // onEnter/onAction/... methods that will only be triggered when the condition is true
  • Added new untilIdentityChanges block. This allows to give a state object an identity like an id and will re-trigger anything running in that block whenever the identity changes.
    spec {
      inState<MyState> {
        // general onEnter/onAction/... methods
        untilIdentityChanges({ state -> state.searchQuery }) { 
          // triggered whenever `searchQuery` changes
          onEnterEffect { state ->
          // whenever `searchQuery` changes the collection is stopped and a new flow is built and collected
          collectWhileInState({ state -> loadSearchResults(state.searchQuery )}) { result, state ->
            // update state based on result

Internal re-write

  • The internals of FlowRedux have been completely rewritten and simplified. The library behavior is now much more consistent and predictable.
  • Cancellation of a running block like collectWhileInState is now guaranteed to happen before anything in the new state starts.

Other changes

  • The collectWhileInState method that has a lambda parameter to build the collected Flow. now receives S instead of Flow<S> as its parameter.
  • The compose artifact is now a multiplatform library with support for all platform supported by compose-multiplatform.


  • inState with additionalIsInState has been deprecated in favor of the condition block.
  • inStateWithCondition has been deprecated in favor of the condition block.

1.1.0 (2022-05-08)

  • Updated to Kotlin 1.8.21 and Coroutines 1.7.0.
  • Added support for Kotlin/JS
  • Added support for all tier 1, 2 and 3 Kotlin/Native targets
  • Removed the @FlowPreview opt in annotation, @ExperimentalCoroutinesApi is still required.
  • The sub state machine DSL methods now take StateMachine instead of FlowReduxStateMachine as parameter. This allows using different kinds of state machines together with FlowRedux which might ease migrating a state machine to FlowRedux.
  • A few methods which already had reified overloads are now hidden from auto complete (this change is binary compatible).
  • Fixed race condition when using sub state machines that could cause a crash when an action is dispatched shortly after the sub state machine starts.

1.0.2 (2022-11-15)

  • Support optional values in the actionMapper of sub state machines. When the mapper returns null the action won’t be forwarded which removes the need to either handle all actions in the sub state machine or introduce a no op action.

1.0.1 (2022-11-04)

  • Dependency updates

1.0.0 (2022-07-06)

  • Remove deprecated ChangeState and other (deprecated friends)
  • Add DSL marker
  • Restructure, update and extend docs

0.13.0 (2022-06-13)

New State object

Previously all the methods in the DSL had a stateSnapshot: YourStateClass parameter, which represented the state machine’s current state at the time the DSL method was called. For all non effect methods this parameter is now replaces by a state parameter that looks like this state: State<YourStateClass>. The new State class has a snapshot allowing access to the same value that you received before. It also has .mutate { } (returns the same type as the current state, usually used with copy), .override { } (to transition to another state subclass) and .noChange { } methods to create the ChangeState objects. So instead of doing MutateState { ... } you should now do state.mutate { ... }.

This has a few advantages: - State knows about the InputState type so it’s not possible anymore to accidentally create MutateState instances with the wrong input type, this is now enforced by the type system, before it would have crashed at runtime - it’s also not necessary anymore to specify the type parameters for mutate state, the generics are inferred

Lambdas in the DSL

We now recommend to use lambdas instead of method references in the flow redux DSL (e.g. on<ButtonClicked> { action, state -> transitionToSomeState(action, state) } over on(::buttonClicked/on(::transitionToSomeState)) because: - Parameters of the reference are required to be there but the compiler warns when they are unused, in a lambda you can just use _ and remove the parameter from the method. - The function name should describe what it does (doSomething) but in practice we usually see it being named after the action (e.g. on(::buttonClicked)). The assumption is that if you have on<ButtonClicked> { ... } you are less inclined to call the method buttonClicked as well. - An addition to the above is that if you do on(::doSomething) you lose the information of when it happens while on<ButtonClicked> { transitionToSomeState(it) } would make getting an overview easier. Of course you can combine both in your function name but that leads to long/weird names. For example onButtonClickedTransitionToSomeState is long and would then result in on(::on...) while leaving out the on from the method name reads weirdly when looking at just the function. - Method references don’t work well when the method has a dependency. In practice the function is just put into the state machine class which means it’s not testable on its own anymore. While we introduced functional interfaces in [#189].( to make this easier, they are also a lot more verbose. If you just call a method from the lambda you can pass additional parameters to it and it keeps the syntax more aligned. - In some circumstances (not sure when it happens) the IDE can’t really auto complete the referenced function when you’re writing ::...

Other changes - Renamed stateMachine DSL method to onEnterStartStateMachine - initialStateSupplier is now called whenever the state collection starts - The initial state in the compose integration is now null - Don’t swallow ClassCastExceptions from the handler - The state machine will now throw an exception when state is collecting more than once at the same time #308 - ChangeState.reduce is now public for testing purposes #309

0.12.0 (2022-03-21)

Breaking changes:

  • Removed dsl artifact (and gradle module).FlowReduxStateMachine and all DSL stuff now lives inside flowredux artifact. Change your maven coordintaes from com.freeletics.flowredux:dsl:0.11.0 to com.freeletics.flowredux:flowredux:0.12.0. Package names renamed the same so no breaking change at code level. This is just a breaking change at artifact and packaging level.
  • Removes Logger as we don’t need it


  • Add usage of atomic variables
  • remove obsolete experimental annotations

0.11.0 (2021-11-23)


  • Convenience artefact to work with jetpack compose: FlowReduxStateMachine.rememberStateAndDispatch()
val stateMachine = MyFlowReduxStateMachine()

fun MyUi(){
  val (state, dispatch) = stateMachine.rememberStateAndDispatch()
  • Overload for sub-statemachine

0.10.0 (2021-10-27)

New: - support for composable child state machines - Support for Apple Silicon targets - Added a check that throws an exception if FlowReduxStateMachine.dispatch(action) is called before collecting FlowReduxStateMachine.state

Breaking API change: - FlatMapPolicy is renamed to ExecutionPolicy

Fix: - fix a crash caused by resubscribing to a state machine (introduced in 0.9.0)

0.9.0 (2021-10-20)

Breaking API changes: - FlowReduxStateMachine is not using StateFlow anymore. That makes the Statemachine “cold” again.

Addition: - Turned type alias for DSL lambdas into fun interface

0.8.0 (2021-08-25)

New: - Introduced onActionEffect, onEnterEffect and onCollectWhileInStateEffect to do some work as a sort of “side effect” without changing the state - Introduced collectWhileInState(flowBuilder: (Flow<State> -> Flow<Value>) - Overloads for collectWhileInstate and on<Action> to pass in function references without the need of specifying FlatMapPolicy or explicitly use named argument for handler.

0.7.0 (2021-08-02)

A bunch of Bug fixes, please update!

Fixes: - Cancel onEnter block if state is left - Cancel onAction block if state is left - Cancel collectWhileInState block if state is left - Fixed unit tests to run with multithreaded dispatcher

API changes: - Removed FlatMapPolicy from onEnter - Removed collectWhileInAnyState. Use inState<RootClassFromStateHierarchy> { collectWhileInState(flow) {... } } instead to get to the same endresult.

0.6.0 (2021-06-21)

  • Some internal improvements mainly around removing Channel and replacing it with MutableSharedFlow

0.5.0 (2021-05-12)

This is a major change and milestone towards 1.0 release

This release contains breaking changes

  • ChangeState is return type for all DSL blocks such as onEnter{ ... }. It replaces setState{ ... } to trigger state transitions. Furthermore, this allows us to easily write functions that can be unit tested more easy compared to how it worked before (setState and ‘getState’). A function signature i.e. to handle an action looks as follows: fun handleAction(action : MyAction, stateSnapshot : MyState) : ChangeState<State>
  • getState' has been removed as it's not needed anymore becauseChangeState` replaces it.
  • inStateWithCondition replaces `inState(condition : (State) -> Boolean)’ to avoid issues with overloads and type erasure on jvm.

0.4.0 (2020-10-01)

  • Compiled with Kotlin 1.4.10 (binary compatible with Kotlin 1.4.0)

Breaking change

Artifact coordinates did change: For multiplatform are from now on

implementation 'com.freeletics.flowredux:flowredux:0.4.0'
implementation 'com.freeletics.flowredux:dsl:0.4.0'
and for jvm:
implementation 'com.freeletics.flowredux:flowredux-jvm:0.4.0'
implementation 'com.freeletics.flowredux:dsl-jvm:0.4.0'
This is more streamlined now with kotlin multiplatform library packaging best practices.

0.3.0 (2020-02-14)

New - Added setState (runIf: (State) -> Boolean ) { ... } where in runIf you can specify if this setState block should actually run or not. Per default it will only run if you are still in the state specified in inState - Added a generic way to define inState(isInState = (State) -> Boolean) { ... } in addintion to isInState<State>.

Breaking changes - Renamed observeWhileInState to collectWhileInState() #63 - Renamed observe() to collectInAnyState() - Renamed type alias StateAccessor to GetState

Improvement - Don’t package test libraries in jvm dsl jar artifact #54

0.2.1 (2020-02-02)

  • Multiplatform release for iOS, jvm, watchOS and TvOS. JavaScript not included yet.
  • Renamed library artifact to flowredux
  • introduces inState<> { onEnter() } to DSL
  • Added a sample app for android and iOS (using SwiftUI).

0.1.0 (2019-10-24)

First official release targeting JVM only (Multiplatform coming soon). Contains

  • FlowrRedux: the core library (think of it as the low level API)
  • FlowRedux-DSL: A fluend DSL to describe your ReduxStore (think of it as the high level API)l