Building async. running Kotlin Multiplatform state machine made easy with a DSL and coroutines.

Usage

Full documentation and best practices can be found here: https://freeletics.github.io/FlowRedux/

sealed interface State

object Loading : State
data class ContentState(val items : List<Item>) : State
data class Error(val error : Throwable) : State


sealed interface Action
object RetryLoadingAction : Action


class MyStateMachine : FlowReduxStateMachine<State, Action>(initialState = Loading){
    init {
        spec {
            inState<Loading> {
                onEnter { state : State<Loading> ->
                    // executes this block whenever we enter Loading state
                    try {
                        val items = loadItems() // suspending function / coroutine to load items
                        state.override { ContentState(items) } // Transition to ContentState
                    } catch (t : Throwable) {
                        state.override { Error(t) } // Transition to Error state
                    }
                }
            }

            inState<Error> {
                on<RetryLoadingAction> { action : RetryLoadingAction, state : State<Error> ->
                    // executes this block whenever Error state is current state and RetryLoadingAction is emitted
                    state.override { Loading } // Transition to Loading state which loads list again
                 }
            }

            inState<ContentState> {
                collectWhileInState( flowOf(1,2,3) ) { value : Int, state : State<ContentState> ->
                    // observes the given flow as long as state is ContentState.
                    // Once state is changed to another state the flow will automatically
                    // stop emitting.
                    state.mutate {
                        copy( items = this.items + Item("New item $value"))
                    }
                }
            }
        }
    }
}

val statemachine = MyStateMachine()

launch {  // Launch a coroutine
    statemachine.state.collect { state ->
      // do something with new state like update UI
      renderUI(state)
    }
}

// emit an Action
launch { // Launch a coroutine
    statemachine.dispatch(action)
}

In an Android Application you could use it with AndroidX ViewModel like that:

class MyViewModel @Inject constructor(private val stateMachine : MyStateMachine) : ViewModel() {
    val state = MutableLiveData<State>()

    init {
        viewModelScope.launch { // automatically canceled once ViewModel lifecycle reached destroyed.
            stateMachine.state.collect { newState ->
                state.value = newState
            }
        }
    }

    fun dispatch(action : Action) {
        viewModelScope.launch {
            stateMachine.dispatch(action)
        }
    }
}

Dependencies

There are two artifacts that you can include as dependencis:

1. flowredux: this is the core library and includes the DSL.
2. compose: contains some convenient extensions to work with FlowReduxStateMachine in Jetpack Compose.

JVM / Android only

implementation 'com.freeletics.flowredux:flowredux-jvm:<latest-version>'
implementation 'com.freeletics.flowredux:compose:<latest-version>'

Multiplatform

implementation 'com.freeletics.flowredux:flowredux:<latest-version>'

FlowRedux is supported on:

• JVM / Android
• iOS
• watchOS
• tvOS
• macOS
• Linux
• Windows

We do plan to add support for JavaScript but it’s not available yet.

Snapshot

Latest snapshot (directly published from main branch from CI on each change):

allprojects {
    repositories {
        // Your repositories.
        // ...
        // Add url to snapshot repository
        maven {
            url "https://oss.sonatype.org/content/repositories/snapshots/"
        }
    }
}

Then just use -SNAPSHOTsuffix as version name like

implementation 'com.freeletics.flowredux:flowredux:1.2.1-SNAPSHOT'