Framework library for developing applications using a unidirectional data flow model. Features include state management, rendering, actions, effects, and loop handling for seamless UI updates.
This is a Kotlin Multiplatform framework library for developing applications on the JVM, JavaScript and Android based on the unidirectional dataflow model. The basic idea can be considered as an MVI architecture with reducer, but without the reducer.
flowchart LR
A[First State] -->|Input| B{Action} -->|Mutate| C(Model) --> D[Renderer] -->|Derive| E[Next State] -.->|Input| B
B -->|Trigger| F([Effect]) --> B
Please click here for generated documentation.
This brief example is missing some glue code to provide a quick feel of the library mechanics.
Packages are published to Maven Central, so make sure to add it to your list of repositories.
repositories {
mavenCentral()
}
dependencies {
// core multiplatform package (added transitively when using the compose package below)
implementation("com.ekezet.hurok:hurok-base:3.2.0")
// library for using hurok with Compose Multiplatform
implementation("com.ekezet.hurok:hurok-compose:3.2.0")
// library for testing hurok-based applications
testImplementation("com.ekezet.hurok:hurok-test:3.2.0")
}
[versions]
hurok = "3.2.0"
[libraries]
hurok-base = { group = "com.ekezet.hurok", name = "hurok-base", version.ref = "hurok" }
hurok-compose = { group = "com.ekezet.hurok", name = , version.ref = }
= { group = , name = , version.ref = }
= [, ]
dependencies {
implementation(libs.bundles.hurok)
testImplementation(libs.hurok.test)
}
For code samples please see Othello for Android.
// Data model for business logic
data class ScoreScreenModel(
val user: User? = null,
val isLoading: Boolean = false,
val throwable: Throwable? = null,
)
// State for representation
data class ScoreScreenState(
val playerName: String,
val score: String,
val isLoading: Boolean,
val errorMessage: String?,
)
// Renderer converts the model into a state
class ScoreScreenRenderer : Renderer<ScoreScreenState, ScoreScreenModel> {
fun renderState(model: ScoreScreenModel) = with(model) {
ScoreScreenState(
playerName = if (user == null) "N/A" else user.nickname,
score = if (user == null) "N/A" else user.score.roundToInt().toString(),
errorMessage = throwable?.run { message ?: "Unknown error" },
isLoading = isLoading,
)
}
}
fun ScoreScreenView(args: ScoreScreenArgs?) {
// Wraps a loop as a @Composable
// ...or there's the lifecycle-aware LoopViewWithLifecycle() on Android
LoopView(
builder = ScoreScreenLoop,
args = args,
) { emit ->
Column {
if (isLoading) {
Text("Loading...")
} else if (errorMessage != null) {
Text(errorMessage)
// Buttons emit an update action
Button(onClick = { emit(OnUpdateScoreClick) }) {
Text("Retry")
}
} else {
Text(playerName)
Text(score)
Button(onClick = { emit(OnUpdateScoreClick) }) {
Text("Update score")
}
}
}
}
}
// Action to start updating the score on user click
data object OnUpdateScoreClick : ScoreScreenAction {
override fun ScoreScreenModel.proceed() =
next(copy(isLoading = true, throwable = null), UpdateScore(user.id))
}
// Action on successful update
data class UpdateScoreSuccess(val user: User) : ScoreScreenAction {
override fun ScoreScreenModel.proceed() =
next(copy(user = user, isLoading = false))
}
// Action on update failure
data class UpdateScoreError(val throwable: Throwable) : ScoreScreenAction {
override fun ScoreScreenModel.proceed() =
next(copy(throwable = throwable, isLoading = false))
}
// Background side effect for updating the data
data class UpdateScore(val userId: String) : ScoreScreenEffect {
override suspend fun ScoreScreenEmitter.trigger(dependency: ScoreScreenDependencv) {
try {
val user = scoreService.getUserScore(userId)
emit(UpdateScoreSuccess(user))
} catch (throwable: Throwable) {
emit(UpdateScoreError(throwable))
}
}
}
| Name | Description |
|---|
| State | Loop state derived from the Model |
| Model | Holds data for business logic |
| Args | A way to pass inputs to an existing Loop |
| ArgsApplyer | Applies arguments to the Model |
| Renderer | Uses the Model to create new State |
| Action | Mutates the Model and can trigger (any) Effect |
| Effect | Does background work and triggers (any) Action |
| Loop | Glue that holds the parts together |
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