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Redux-Kotlin

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A redux standard for Kotlin that supports multiplatform projects.

Full documentation at http://reduxkotlin.org.

Misson Statement

Provide a standard redux implementation for Kotlin. In doing so will foster a ecosystem of middleware, store enhancers, & dev tools. These core values will guide descisions for the project:

  • core redux-kotlin will be a minimal implementation that other libraries can build upon
  • modular development (follow example of https://github.com/reduxjs)
  • support for all platforms supported by Kotlin multiplatform (JVM, iOS, Native, JS, WASM)
  • developed in open and enable discussion for all interested parties via open channels (slack, github, etc. TBD)
  • not owned by a individual or company

Redux in Kotlin, and in mobile in particular, may differ a bit from javascript. Many have found the basic pattern useful on Android & iOS leading to tens of opensource redux libraries in Kotlin, Java, and Swift, yet an ecosystem has yet to emerge. A port of javascript redux is a good starting point for creating a standard and will aid in cross-pollination of middleware, store enhancers, & dev tools from the javascript world.

Redux has proven helpful for state management in mobile. A multiplatform Kotlin implementation & ecosystem will increase developer productivity and code reuse across platforms.

Droidcon NYC Slides Video TBA

*** PLEASE FILL OUT THE Redux on Mobile Survey ***

How to add to project:

Artifacts are hosted on maven central. They are published with gradle metadata, so you may need to enable with enableFeaturePreview("GRADLE_METADATA") in your settings.gradle file. For multiplatform, add the following to your shared module:

kotlin {
  sourceSets {
        commonMain { //   <---  name may vary on your project
            dependencies {
                implementation "org.reduxkotlin:redux-kotlin-threadsafe:0.5.5"
            }
        }
 }

For JVM only:

  implementation "org.reduxkotlin:redux-kotlin-threadsafe-jvm:0.5.5"

*Non threadsafe store is available. Typical usage will be with the threadsafe store. More info read here

Usage is very similar to JS Redux and those docs will be useful https://redux.js.org/. These docs are not an intro to Redux, and just documentation on Kotlin specific bits. For more info on Redux in general, check out https://redux.js.org/.

Create an AppState class

  data class AppState(val user: User, val feed: List<Feed>)

Create Reducers:

  val reducer: Reducer<AppState> =  { state, action ->
    when (action) {
        is UserLoggedInAction -> state.copy(user = action.user)
        ...
    }
  }

Create Middleware: There are a few ways to create middleware:

Using a curried function stored in a val/var:

  val loggingMiddleware: Middleware = 
          { store ->
              { next ->
                  { action ->
                        //log here
                        next(action)
                   }
               }
            }

Using a function:

  fun loggingMiddleware(store: Store) = { next: Dispatcher -> 
              { action: Any -> 
                     //log here
                     next(action)
               }

Using the convenience helper function middleware:

   val loggingMiddleware = middleware { store, next, action -> 
          //log here
          next(action)
          }

Create a store

  val store = createStore(reducer, AppState(user, listOf()), applyMiddleware(loggingMiddleware))

You then will have access to dispatch and subscribe functions from the store.

Create a synchronized store

  val store = createThreadSafeStore(reducer, AppState(user, listOf()), applyMiddleware(loggingMiddleware))

Access to store methods like dispatch and getState will be synchronized. Note: if using a thread safe store with enhancers or middleware that require access to store methods, see usage below.

Create a synchronized store using an enhancer

 val store = createStore(reducer, AppState(user, listOf(), compose(
    applyMiddleware(createThunkMiddleware(), loggingMiddleware),
    createSynchronizedStoreEnhancer() // needs to be placed after enhancers that requires synchronized store methods
 ))

Access to store methods like dispatch and getState will be synchronized, and enhancers (eg. applyMiddleware) that are placed above createSynchronizedStoreEnhancer in the enhancer composition chain will receive the synchronized store.

Communication

Want to give feedback, contribute, or ask questions?

#redux slack channel in kotlinlang

Trello boards - https://trello.com/reduxkotlinorg

Or create an issue on github.