kotlin-redux

Kotlin wrapper for Redux library. Major version number of this wrapper matches that of Redux itself.

Creating and using a store in Kotlin

In Redux, the store is an object that contains state, which could be anything. In Kotlin, this is no different. Just note that you must specify the preloaded state. Also, it is encouraged that you use the rEnhancer function to adapt Redux to Kotlin.

val myStore = createStore(::myReducer, someState, rEnhancer())

Access the state via the store's state field.

myStore.state

If you are using rEnhancer, Actions can be implemented as classes. Just implement the RAction interface.

class MyAction : RAction

Writing reducers is easy, too:

fun myReducer(state: TypeOfState, action: RAction) = when (action) {
    is MyAction -> someNewState
    else -> state
}

You can now dispatch the action as usual.

myStore.dispatch(MyAction())

Subscribing to your store works as usual.

val unsubscribe = myStore.subscribe { println(myStore.state) }

Middleware

Middleware works as usual. However, if you are using rEnhancer, it is important to keep in mind the order in which you compose rEnhancer and applyMiddleware. If you specify rEnhancer first, then your middleware will be passed actions that rEnhancer has already processed. If you specify rEnhancer last, it will be passed your unprocessed RActions.

compose(rEnhancer(), applyMiddleware(someMiddleware)) // Middleware works with standard actions

compose(applyMiddleware(someMiddleware), rEnhancer()) // Middleware works with RActions

Serialization

If you need to serialize RActions to JSON, you can do so using kotlinx.serialization. Just mark the actions you want to serialize with @Serializable, and you can serialize and deserialize them in a type-safe manner using serializeAction() and deserializeAction():

val jsonAction = serializeAction(MyAction())

val action = when (Json.parse((StringSerializer to StringSerializer).map, jsonAction)["type"]) {
	"MyAction" -> deserializeAction<MyAction>(jsonAction)
	"MyOtherAction" -> deserializeAction<MyOtherAction>(jsonAction)
	else -> null
}

Limitations

Note that combineReducers will convert any Kotlin lists to JavaScript arrays without Kotlin's type system noticing, which can cause all sorts of nasty errors. If you are using combineReducers, make sure to use arrays and not lists in your state.

Tutorial

See lawik123/kotlin-poc-frontend-react-redux. This project is an implementation/translation of the react-redux Todo List example project in Kotlin (with the addition of react-router).