A library that allows you to share ViewModels between Android and iOS.

The latest version of the library uses Kotlin version 1.8.20.
Compatibility versions for newer Kotlin versions are also available:

Add the library to your shared Kotlin module:

dependencies {
    implementation("com.rickclephas.kmm:kmm-viewmodel-core:<version>")
}

Create your ViewModels almost as you would in Android:

import com.rickclephas.kmm.viewmodel.KMMViewModel
import com.rickclephas.kmm.viewmodel.MutableStateFlow
import com.rickclephas.kmm.viewmodel.stateIn

// 1: use KMMViewModel instead of ViewModel
open class TimeTravelViewModel: KMMViewModel() {

    private val clockTime = Clock.time

    /**
     * A [StateFlow] that emits the actual time.
     */
    val actualTime = clockTime.map { formatTime(it) }
        // 2: supply viewModelScope to your stateIn calls
        .stateIn(viewModelScope, SharingStarted.WhileSubscribed(), "N/A")

    // 3: supply viewModelScope to your MutableStateFlows
    private val _travelEffect = MutableStateFlow<TravelEffect?>(viewModelScope, null)
    /**
     * A [StateFlow] that emits the applied [TravelEffect].
     */
    val travelEffect = _travelEffect.asStateFlow()
}

You need to use viewModelScope wherever possible to propagate state changes to iOS.
In other cases you can access the ViewModelScope.coroutineScope property directly.

Use the @NativeCoroutinesState annotation from KMP-NativeCoroutines to turn your StateFlows into properties in Swift:

@NativeCoroutinesState
val travelEffect = _travelEffect.asStateFlow()

Checkout the README for more information and installation instructions for KMP-NativeCoroutines.

val TimeTravelViewModel.travelEffectValue: TravelEffect?
    get() = travelEffect.value

Add the library to your Android module:

dependencies {
    implementation("com.rickclephas.kmm:kmm-viewmodel-core:<version>")
}

Use the view model like you would any other Android view model:

class TimeTravelFragment: Fragment(R.layout.fragment_time_travel) {
    private val viewModel: TimeTravelViewModel by viewModels()
}

Note: support for Jetpack Compose is coming soon.

Add the Swift package to your Package.swift file:

dependencies: [
    .package(url: "https://github.com/rickclephas/KMM-ViewModel.git", from: "<version>")
]

Or add it in Xcode by going to File > Add Packages... and providing the URL: https://github.com/rickclephas/KMM-ViewModel.git.

Create a KMMViewModel.swift file with the following contents:

import KMMViewModelCore
import shared // This should be your shared KMM module

extension Kmm_viewmodel_coreKMMViewModel: KMMViewModel { }

After that you can use your view model almost as if it were an ObservableObject.
Just use the view model specific property wrappers and functions:

E.g. to use the TimeTravelViewModel as a StateObject:

import SwiftUI
import KMMViewModelSwiftUI
import shared // This should be your shared KMM module

struct ContentView: View {
    @StateViewModel var viewModel = TimeTravelViewModel()
}

It's also possible to subclass your view model in Swift:

import Combine
import shared // This should be your shared KMM module

class TimeTravelViewModel: shared.TimeTravelViewModel {
    @Published var isResetDisabled: Bool = false
}