Facilitates easy observation of state changes in Jetpack Compose and SwiftUI with minimal boilerplate using the `StateHolder` interface for seamless UI state management. Offers automatic Swift wrapper generation.
Make state defined in KMM shared module easy to observe within Jetpack Compose and SwiftUI code with near zero
boilerplate by implementation of StateHolder interface on class providing state to UI.
flowchart RL
subgraph KMM Shared Module
StateHolder
end
subgraph iOS/Android
View
end
StateHolder -- state --> View
View -- event --> StateHolder
Define a ViewModel, Store or whatever implementing a StateHolder interface inside your shared module. Use it in
the platform.
class SimpleViewModel : KmmViewModel(), StateHolder by StateHolder() {
var message by stateful("Hello World")
private set
fun updateMessage() = viewModelScope.launch {
delay(500)
message = "Hello k-state"
}
}
Add kstate-core dependency to the commonMain source set.
val commonMain by getting {
dependencies {
implementation("com.jstarczewski.kstate:kstate-core:0.0.3")
}
}
Depending on the architecture consider exporting the library.
Add kstate.generate gradle plugin to proper gradle module to generate Swift wrappers.
plugins {
id("com.jstarczewski.kstate.generate").version("0.0.3")
}
Configure wrappers by kstate.generate DSL syntax.
swiftTemplates {
outputDir = "../ios/ios/StateHolder"
sharedModuleName = "common"
coreLibraryExported = false
}
Generate templates for iOS app by executing following gradle task.
./gradlew generateSwiftTemplates
After generation the plugin is no longer needed and can be safely removed from the project configuration.
Documentation is available here.
Samples are available as an example app on GitHub.
StateHolder by implementing StateHolder interface via interface delegation
pattern with StateHolder() function.StateHolder DSL functions to declare Stateful in shared StateHolder with delegate.class SimpleViewModel : KmmViewModel(), StateHolder by StateHolder() {
var message by stateful("Hello World")
private set
fun updateMessage() = viewModelScope.launch {
delay(500)
message = "Hello k-state"
}
}
State changes in @Composable functions are reflected because shared State on Android platform is exposed as
Compose MutableState
@Composable
fun SimpleScreen() {
val viewModel: SimpleViewModel = viewModel { SimpleViewModel() }
Box(modifier = Modifier.fillMaxSize()) {
Greeting(
modifier = Modifier
.align(Alignment.Center)
.clickable { viewModel.updateMessage() },
text = viewModel.message
)
}
}
Apply ObservedStateHolder property wrapper to SimpleViewModel to automatically wire state change observation.
ObservedStateHolder is a utility property wrapper that will be generated
during library setup process.
struct SimpleView: View {
@ObservedStateHolder var viewModel = SimpleViewModel()
var body: some View {
Text(viewModel.message)
.onTapGesture {
viewModel.updateMessage()
}
}
}
kstate-core libraryDepending on whether the for sake of the project architecture the kstate-core library should be
exported or not
additional templates setup may be needed.
The default behaviour is that the kstate-core is not exported and no further configuration is needed, but for
exported kstate-core where the export example is contained withing the following snippet of build.gradle.kts file.
kotlin {
android()
listOf(
iosX64(),
iosArm64(),
iosSimulatorArm64()
) {
it {
baseName = "common"
(project(":feature:saveable"))
(project(":feature:obtainable"))
("com.jstarczewski.kstate:kstate-core:.")
}
}
sourceSets {
val commonTest by getting
val commonMain by getting {
dependencies {
(kotlin("test"))
(project(":feature:saveable"))
(project(":feature:obtainable"))
("com.jstarczewski.kstate:kstate-core:.")
}
}
Templates need extra configuration to work. Add the following coreLibraryExported flag set to true
to swiftTempaltes config.
plugins {
id("com.jstarczewski.kstate.generate").version("0.0.3")
}
swiftTemplates {
outputDir = "../ios/ios/StateHolder"
sharedModuleName = "common"
// On default it is set to false
coreLibraryExported = true
}
After successfully applying the plugin configuration, generate Swift wrappers. Files should appear in outputDir
specified in
configuration
block.
./gradlew generateSwiftTemplates
To link generated files with your project, from XCode File menu click Add files and create group with sources.
When the files are linked, run the iOS app to check whether everything builds. Maybe there are additional changes
needed to be done in the files, but
the vision is that after linking generated sources iOS app should build without anny issues.
The generation process is a one time operation. After successfully generating everything feel free to add it to source
control and remove kstate-generate plugin
statefulSurfaced from shared tags and platforms — no rankings paid for.