Redux powered Android Dev

Me

Mobile Enthusiast (Android / iOS)

Love Kotlin / Swift + Opensource projects

Join mercari (merpay) in 2018 :)

github.com/kittinunf

@kittinunf

Yet another architecture?

Programming is abstraction

data class Car(
  val make: String, 
  val wheel: Int, 
  val color: Color
)

val car1 = Car("Honda", 4, Color.WHITE)

val car2 = Car("Toyota", 8, Color.RED)

State?

class View {
  // 3 VISIBLE, INVISIBLE, GONE
  var visibility: Int,
  // 2 focused, not
  var focused: Boolean,
  // 2 activated, not
  var activated: Boolean,
   // 2 enabled, not
  var enabled: Boolean
}
// possibility 3 * 2 * 2 * 2

MV(P)(VM)

        view.chatListSignals
          .map { itemCount -> itemCount == 0 }
          .subscribe { emptyList ->
            view.setChatListViewVisibility(if (emptyList) GONE else VISIBLE)
            view.showEmptyState(emptyList)
        }.addTo(disposables)

        paginator.results.subscribe { response ->
            showConversationResults(response)
        }.addTo(disposables)

        paginator.errors
                .subscribe(view::showError)
                .addTo(disposables)

        view.onLoadMoreSignals.subscribe {
            paginator.loadNext()
        }.addTo(disposables)

        view.onDeleteSignal
                .flatMap { chatMembership -> repository.leaveChat(chatMembership.chat.id) }
                .filter { response -> !response.isSuccessful }
                .subscribe(view::showError)
                .addTo(disposables)

        view.onLeaveSignal
                .flatMap { chatMembership -> repository.leaveChat(chatMembership.chat.id) }
                .filter { response -> !response.isSuccessful }
                .subscribe(view::showError)
                .addTo(disposables)

State is easy

But maintaining state is quite hard

Then, why not use abstraction that is serious about maintaining the state?

Idea of Redux

3 Principles of Redux

Redux attempts to make the state mutation predictable

Single source of truth

State is read only

Changes made with pure function

Idea of Redux

Action

State

Store

Reducer

Action

Payload of information from User / Screen to Store

sealed class Action

class Load : Action
class ShowResult(list: List<Data>) : Action
class ShowError(error: String) : Action

State

A single source of truth to represent the screen

data class State(
  // represent list of data on the screen
  data: List<Data>, 
  loading: Boolean,
  error: String?
)

// or you can do even better with sealed class
sealed class State

object Loading : State
class Success(list: List<Data>)
class Failure(reason: String)

Reducer

Pure function where we change our State

val reducer = object : Reducer<State> {
  override fun reduce(currentState: State, action: Action):
    State {
    
    return when (action) { 
      Loading -> currentState.copy(loading = true)
      is ShowResult -> currentState.copy(
                         list = action.list, 
                         loading = false
                       )  
      is ShowError -> currentState.copy(
                         error = action.reason, 
                         loading = false
                       )
    }
  }
}

Store

Store is where the things get connecting, glues everything together

Store

Reducer

View (consumer)

Update your view in predictable way

 

store.states.subscribe { state ->
  // state is a snapshot of thing on the screen 
  // at any point in time
  
  if (loading == true) {
    recyclerView.setVisibility = View.GONE
    loadingView.setVisibility = View.VISIBLE
  } else {
    recyclerView.setVisibility = View.VISIBLE
    loadingView.setVisibility = View.GONE

    adapter.update(state.list)
    adapter.notifyDataSetChanged()
  }
  
}

Fits everything together

Store

Reducer

State (new)

State

Action

Wait you don't tell me what the Library you use?

To be honest, you could just write your own

I wrote my own for today's demo

DEMO

Devtools?

What if I am telling you that we can do that™ with AS

Demo again?

Q & A

Redux Powered Android Dev

By Kittinun Vantasin

Redux Powered Android Dev

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