kotlin - 用多个扩展密封类替换枚举

Question

目前我有三个枚举类代表我的状态机中的状态和一个显示操作

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
    }
}

我想将我当前的实现更改为密封类。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......

有没有办法使用密封类来知道当前的 OperationStatus 是什么而不将 State 映射到它？

Answer 1

这对我有用

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)
}

请注意，State.OperationState...除非您进行导入，否则您is必须when指定整个类型名称（第一个 ( ) 不需要它，FirstState.A因为您正在与特定的单例对象进行比较，因此您希望它看起来如何