用多个扩展密封类替换enum

Question

目前，我有三个枚举类表示状态机中的状态，其中一个用于显示操作

interface State
enum class OperationState : State {
InProgress,
Finished,
Error
}
enum class FirstState : State {
//some states
}
enum class  NextState: State {
//some states
}
enum class  LastState: State {
//some states
}

在我的服务中，我有：

when (state) {
is FirstState -> {
//do something
changeFirstStateOperationState(state)
}
is NextState -> {
//do something
changeNextStateOperationState(state)
}
is LastState -> {
//do something
changeLastStateOperationState(state)
}
}
private fun changeFirstStateOperationState(state: FirstState){
when(state){
FirstState.A -> OperationState.Error
listOf(FirstState.B, FirstState.C) -> OperationState.InProgress
FirstState.D -> OperationState.Finished
}
}

我想把我现在的实现改为密封类。我试过类似的东西：

sealed class State {
sealed class OperationState : State() {
sealed class FirstState : OperationState() {
object A: FirstState()
object B: FirstState()
object C: FirstState()
object D: FirstState()
}
sealed class NextState:OperationState(){ ... }
sealed class LastState:OperationState(){ ... }
}
}

但它不起作用。。。

有没有任何方法，使用密封类，在不将State映射到它的情况下，知道当前OperationStatus是什么？

Answer 1

这适用于我的

sealed class State {
sealed class OperationState : State() {
sealed class FirstState : OperationState() {
object A: FirstState()
object B: FirstState()
object C: FirstState()
object D: FirstState()
}
sealed class NextState:OperationState(){ }
sealed class LastState:OperationState(){ }
}
}
fun main() {
checkState(State.OperationState.FirstState.A)
}
fun checkState(state: State) {
when(state) {
is State.OperationState.FirstState.A -> "it's A"
is State.OperationState.FirstState -> "it's another FirstState"
is State.OperationState.NextState -> "it's a NextState"
is State.OperationState.LastState -> "LastState"
}.run(::println)
}

只需注意，除非进行导入(如果嵌套过多，可能建议您这样做(，否则必须指定整个类型名称(State.OperationState...(，而且必须在when匹配器中使用is，因为您在比较类型。第一个对象(FirstState.A(不需要它，因为您正在与特定的单例对象进行比较，所以您希望它看起来如何取决于您