用多个扩展密封替换枚举类

Question

目前我有三个枚举 classes 表示我的状态机中的状态，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
    }
}

我想将我当前的实现更改为密封的 classes。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(){ ... }
    }
}

但是没用...

有没有什么方法可以使用密封的 class 来知道当前的 OperationStatus 而无需将 State 映射到它？

Answer 1

This works for me

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，您必须指定整个类型名称 (State.OperationState...)，除非您进行导入（如果嵌套这么多，可能会推荐），而且您还必须使用 is 在 when 匹配器中，因为您正在比较类型。第一个不需要它 (FirstState.A)，因为你是在与特定的单例对象进行比较，所以它的外观取决于你自己

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