UseCase usage

Define UseCase

UseCase is a abstract class with one abstract suspend function. It has two generic parameters. The first is to define Argument type, the second is to define Return type. If you don't need any of these, just put in z Unit The suspend function will be executed on non-ui thread. Don't forget to freeze() the UseCase in init block. Any properties has to be initialized/injected above the init block because of freezing.

// shared/src/commonMain/../domain/
class GetCoinsListUseCase : UseCase<Unit, List<Coin>>() {
    private val coinStore: CoinStore = CoinStore(RestApiManager, DatabaseManager)

    init {
        freeze()
    }

    override suspend fun build(arg: Unit): List<Coin> {
        val list = coinStore.fetchCoins().coins.map {
            Coin(it.id, it.name, it.icon, it.symbol, it.price)
        }
        return list
    }
}

Execute UseCase

To be able to execute the UseCase you have to be in the scope of CoroutineScopeOwner. On the Android side you can take advantage of viewModelScope from Android Architecture Components (AAC). On the iOS side you can use ArkitektViewModelfrom km-viewmodel. If you need to execute the UseCase outside of ViewModel, e.g. in a Service, you need to implement CoroutineScopeOwner and provide CoroutineScope by yourself.

Usage on Android

Define a BaseViewModel:

// androidApp
import androidx.lifecycle.ViewModel
import androidx.lifecycle.viewModelScope
import app.futured.arkitekt.kmusecases.scope.CoroutineScopeOwner

abstract class BaseViewModel : ViewModel(), CoroutineScopeOwner {

    override val coroutineScope = viewModelScope
}

Execute the UseCase:

// androidApp
class CoinsViewModel : BaseViewModel() {
    private val getCoinsUseCase = GetCoinsListUseCase()

    var coins by mutableStateOf(emptyList<Coin>())
    var isLoading by mutableStateOf(false)

    fun fetchCoins() {
        getCoinsUseCase.execute(Unit) {
            onStart { isLoading = true }
            onSuccess { 
                coins = it
                isLoading = false
            }
            onError {
                isLoading = false    
                println(it.message)
            }
        }
    }
}

Usage on iOS

// iosApp
import shared

class BaseViewModel : Km_viewmodelArkitektViewModel {

    deinit {
        onDestroy()
    }
}

Execute the UseCase:

// iosApp
import shared

class CoinsViewModel : BaseViewModel, ObservableObject {
    @Published var coins = [Coin]()

    private let getCoinsUseCase = GetCoinsListUseCase()

    func getCoins() {
        getCoinsUseCase.execute(self, args: KotlinUnit()) {
            $0.onSuccess { list in
                self.coins = list as [Coin]
            }
            $0.onError { error in
                print(error)
            }
        }
    }
}

FlowUseCase usage

Head out to FlowUseCase section.

Example

Check out the usage in the example