kotlin - 密封类扩展了其他密封类

Question

我正在使用 MVI 模式制作各种状态模型和副作用类。状态模型可以通过扩展收集公共(public)部分的接口(interface)来减少样板代码，但是副作用类不支持扩展，因为它是一个密封类。所以我将 Toast 副作用视为样板代码。我怎样才能摆脱这个Toast副作用样板代码？有没有办法让密封类扩展到其他密封类？

我的状态类:

interface BaseMviState {
    val loaded: Boolean
    val exception: Exception?

    fun isException() = exception != null
}

data class MviJoinState(
    override val loaded: Boolean = false,
    override val exception: Exception? = null,
    val loginResult: Boolean = false,
    val registerResult: Boolean = false,
) : BaseMviState

data class MviRoomCreateState(
    override val loaded: Boolean = false,
    override val exception: Exception? = null,
) : BaseMviState

我的副作用类(class):

sealed class MviJoinSideEffect {
    data class SetupAutoLogin(val user: User) : MviJoinSideEffect()
    data class Toast(val message: String) : MviJoinSideEffect() // boilerplate
}

sealed class MviRoomCreateSideEffect {
    data class Toast(val message: String) : MviRoomCreateSideEffect() // boilerplate
}

Answer 1

我通过在密封类中扩展接口(interface)解决了这个问题，如下所示:

sealed interface BaseEvent {
    data class Toast(val toastMessage: String) : BaseEvent
}

sealed class Event : BaseEvent {
    data class Snackbar(val snackbarMessage: String) : Event()
}

fun main() {
    val event: BaseEvent = Event.Snackbar("Hi")

    when (event) {
        is BaseEvent.Toast -> todo(event.toastMessage)
        is Event.Snackbar -> todo(event.snackbarMessage)
    }
}

fun todo(message: String) {}