Kova

Production-ready MVVM for Kotlin Multiplatform — share everything, render natively.

Kova lets you put all of your app's logic — state, ViewModels, use cases, repositories, DI — in commonMain, and keep only rendering code on each platform: Jetpack Compose on Android, SwiftUI on iOS. Both UIs observe the same ViewModel with idiomatic, main-thread-safe APIs.

┌─────────────────────── shared (Kotlin) ────────────────────────┐
│  Repositories · Use cases · Koin DI · StateViewModel<S, A>     │
│        state: StateFlow<S>       actions: EventFlow<A>         │
└──────────────┬────────────────────────────────┬────────────────┘
               │ collectAsStateWithLifecycle()  │ stateNative (generated)
        ┌──────▼──────┐                  ┌──────▼──────┐
        │   Compose   │                  │   SwiftUI   │
        │ (UI only)   │                  │  (UI only)  │
        └─────────────┘                  └─────────────┘

Kotlin's Flow, StateFlow and coroutines don't survive the Objective-C bridge: Swift sees opaque suspending machinery, callbacks land on random threads, and nothing is cancellable. SKIE fixes this by post-processing the compiled framework with a compiler plugin. Kova takes a different, simpler route with zero compiler magic:

• A tiny runtime (kova-core): NativeFlow / NativeStateFlow / NativeSuspend — closure based, always delivered on the main thread, cancellable from Swift, and auto-cancelled with their owning scope. NativeStateFlow.value is synchronous, so SwiftUI renders the first frame with real state.
• A real ViewModel (kova-viewmodel): StateViewModel<State, Action> built on androidx.lifecycle.ViewModel (multiplatform). On Android it is a Jetpack ViewModel — config changes, viewModelScope, Compose viewModel() all work. On iOS, ViewModelHost gives SwiftUI the same lifecycle contract (onCleared, scope cancellation) via deinit.
• One-shot events done right: EventFlow buffers actions while the UI is detached and delivers each exactly once — no lost snackbars on rotation, no replayed navigation on re-subscribe.
• Codegen where it pays off (kova-ksp): annotate a ViewModel with @NativeExport and every public StateFlow/Flow/EventFlow property gets a generated <name>Native accessor — only in the iOS source sets, only for what you export. No boilerplate, no framework-wide rewriting, fully debuggable generated Kotlin you can read.
• A complete MVVM template (template/): a working Tasks app where the Compose and SwiftUI screens are line-for-line mirrors over one shared ViewModel — clone it and rename.

// build.gradle.kts (shared)
plugins {
    alias(libs.plugins.kotlin.multiplatform)
    alias(libs.plugins.android.library)
    alias(libs.plugins.ksp)
}

kotlin {
    androidTarget()
    listOf(iosArm64(), iosSimulatorArm64(), iosX64()).forEach {
        it.binaries.framework {
            baseName = "Shared"
            isStatic = true
            export("in.sitharaj.kova:kova-core:0.1.0")
            export("in.sitharaj.kova:kova-viewmodel:0.1.0")
            export("org.jetbrains.androidx.lifecycle:lifecycle-viewmodel:2.9.1")
        }
    }
    sourceSets.commonMain.dependencies {
        api("in.sitharaj.kova:kova-core:0.1.0")
        api("in.sitharaj.kova:kova-viewmodel:0.1.0")
        api("in.sitharaj.kova:kova-annotations:0.1.0")
    }
}

dependencies {
    add("kspIosArm64", "in.sitharaj.kova:kova-ksp:0.1.0")
    add("kspIosSimulatorArm64", "in.sitharaj.kova:kova-ksp:0.1.0")
    add("kspIosX64", "in.sitharaj.kova:kova-ksp:0.1.0")
}

data class CounterState(val count: Int = 0)
sealed interface CounterAction { data class Toast(val text: String) : CounterAction }

@NativeExport
class CounterViewModel : StateViewModel<CounterState, CounterAction>(CounterState()) {
    fun increment() = setState { copy(count = count + 1) }

    fun save() = intent {                    // coroutine in viewModelScope, errors -> onError()
        repository.save(currentState.count)  // suspend call
        sendAction(CounterAction.Toast("Saved!"))
    }
}

val state by viewModel.state.collectAsStateWithLifecycle()
LaunchedEffect(viewModel) {
    viewModel.actions.collect { action -> /* snackbar, navigation, ... */ }
}

struct CounterScreen: View {
    @StateObject private var holder = ViewModelHolder { CounterViewModel() }

    var body: some View {
        Observing(holder.viewModel.stateNative) { state in   // generated accessor
            Text("Count: \(state.count)")
        }
        .task {
            for await action in stream(holder.viewModel.actionsNative) { /* toast */ }
        }
    }
}

ViewModelHolder, Observing and FlowState live in the KovaSwift Swift Package (this repo's Package.swift) — add it via SPM. It is framework-agnostic by design; the only per-app piece is a ~40-line bridge file (template/iosApp/iosApp/Kova/KovaBridge.swift) that adapts your framework's NativeStateFlow/ViewModel types to it — copy it once and you're done.

template/ is a complete, buildable MVVM app (Tasks CRUD):

• shared/ — model, repository, Koin modules, TasksViewModel (+ unit tests). All logic.
• androidApp/ — Compose UI only.
• iosApp/ — SwiftUI UI only, Xcode project already wired to build the Kotlin framework.

cd template
./gradlew :androidApp:assembleDebug          # Android
open iosApp/iosApp.xcodeproj                 # iOS — just Run
./gradlew :shared:testDebugUnitTest          # shared ViewModel tests

The template consumes Kova from source via includeBuild(..); in your own project depend on the published artifacts and delete that line from settings.gradle.kts.

1. State is a single immutable data class per screen, exposed as StateFlow.
2. Everything UI-bound arrives on the main thread — subscriptions dispatch to Dispatchers.Main.immediate, on both platforms, always.
3. Every subscription has two lifelines: the Swift/Compose side can cancel, and the viewModelScope cancels on clear. Forgetting one never leaks.
4. Events are not state: one-shot effects go through EventFlow, delivered exactly once, buffered while the UI is away.
5. Nullable flow values are rejected at codegen time (Objective-C generics can't represent them) — model absence inside the state class instead.

On macOS, scripts/publish.sh handles the whole flow with credentials stored in the Keychain (never on disk):

./scripts/publish.sh setup     # one-time: Central Portal token + GPG key → Keychain
./scripts/publish.sh local     # dry run to ~/.m2
./scripts/publish.sh           # signed publish to Maven Central

• Kotlin 2.2.21+, KSP 2.2.21-2.0.5, Gradle 8.14+, AGP 8.9+
• Xcode 15+, iOS 16+ deployment target (SwiftUI NavigationStack)
• JDK 17+

• @NativeExport for suspend functions → generated NativeSuspend accessors
• KSP-generated per-app bridge file (retiring the copied KovaBridge.swift)
• SavedStateHandle support in StateViewModel
• watchOS / tvOS / macOS targets
• Kotlin 2.4 Swift Export backend (true Swift types, no Objective-C bridge) once stable

Apache 2.0 — see LICENSE.