RxFeedback

Kotlin version of RxFeedback

20min video pitch

The simplest architecture for RxJava

    typealias Feedback<State, Event> = (Observable<State>) -> Observable<Event>

    fun <State, Event> system(
            initialState: State,
            reduce: (State, Event) -> State,
            vararg feedback: Feedback<State, Event>
        ): Observable<State>

Why

• Straightforward

  • if it's state -> State
  • if it's a way to modify state -> Event/Command
  • it it's an effect -> encode it into part of state and then design a feedback loop

• Declarative

  • System behavior is first declaratively specified and effects begin after subscribe is called => Compile time proof there are no "unhandled states"

• Debugging is easier

  • A lot of logic is just normal pure function that can be debugged using Android studio debugger, or just printing the commands.

• Can be applied on any level

  • Entire system
  • application (state is stored inside a database, Firebase, Realm)
  • Activity/Fragment/ViewModel(Android Architecture Component) (state is stored inside system operator)
  • inside feedback loop (another system operator inside feedback loop)

• Works awesome with dependency injection

• Testing

  • Reducer is a pure function, just call it and assert results
  • In case effects are being tested -> TestScheduler

• Can model circular dependencies

• Completely separates business logic from effects (Rx).

  • Business logic can be transpiled between platforms (ShiftJS, C++, J2ObjC)

Examples

Simple UI Feedback loop

Observables.system(initialState = 0,
                reduce = { state, event: Event ->
                    when (event) {
                        Event.Increment -> state + 1
                        Event.Decrement -> state - 1
                    }
                },
                scheduler = AndroidSchedulers.mainThread(),
                scheduledFeedback = listOf(
                        bind {
                            val subscriptions = listOf(
                                    it.source.map { it.toString() }.subscribe { label.text = it }
                            )
                            val events = listOf(
                                    RxView.clicks(plus).map { Event.Increment },
                                    RxView.clicks(minus).map { Event.Decrement }
                            )
                            return@bind Bindings(subscriptions, events)
                        }
		)
	)

Play Catch

Simple automatic feedback loop.

Observables.system(
                initialState = State.HumanHasIt,
                reduce = { state, event: Event ->
                    when (event) {
                        Event.ThrowToMachine -> State.MachineHasIt
                        Event.ThrowToHuman -> State.HumanHasIt
                    }
                },
                scheduler = AndroidSchedulers.mainThread(),
                scheduledFeedback = listOf(
                        bindUI,
                        react<State, Unit, Event>(query = { it.machinePitching},
				effects = {
				    Observable.timer(1, TimeUnit.SECONDS, AndroidSchedulers.mainThread())
					    .map { Event.ThrowToHuman }
					    }
			)
                )
	)

Paging

Driver.system(
                initialState = State.empty,
                reduce = { state: State, event: Event -> State.reduce(state, event) },
                feedback = listOf(bindUI,
                        reactSafe<State, String, Event>(
                                query = { it.loadNextPage },
                                effects = {
                                    repositoryService.getSearchRepositoriesResponse(it)
                                            .asSignal(onError = Signal.just(Result.Failure(GitHubServiceError.Offline) as SearchRepositoriesResponse))
                                            .map { Event.Response(it) }
                                }
                        )))

How to include?

Add it in your root build.gradle at the end of repositories:

allprojects {
	repositories {
		...
		maven { url 'https://jitpack.io' }
	}
}

Add the dependency

implementation 'com.github.NoTests:RxFeedback.kt:x.y.z'