是否可以将Kotlin的by-delegation用于现有的类/对象(即an的)？

Question

我有一些专门的类，我想使用Kotlin和Arrow创建，它们将围绕Arrow或monad。我创建了以下代码来使用Kotlin的委托，但我想知道它是否可以简化或使其更地道。如有任何建议，我们将不胜感激。

感谢您的时间和兴趣。

internal data class EitherWrapper<L,R>(private var delegate: Either<L,R>) {
     internal operator fun getValue(thisRef: Any?, property: KProperty<*>): Either<L,R> {
        return delegate
    }

    internal operator fun setValue(thisRef: Any?, property: KProperty<*>, value: Either<L,R>) {
        delegate = value
    }
}

fun main(args: Array<String>) {
    val delegate: Either<Exception, String> = Right("howdy")
    val myeither: Either<Exception, String> by EitherWrapper(delegate)
    println("IsLeft(): ${myeither.isLeft()}")
    println("IsRight(): ${myeither.isRight()}")
}

Answer 1

你的代码是正确的，就我所见，你能做的唯一的改进就是使它泛型，而不是特定的，如下所示：

internal data class DelegateWrapper<T>(private var delegate: T) {
  internal operator fun getValue(thisRef: Any?, property: KProperty<*>): T = 
    delegate

  internal operator fun setValue(thisRef: Any?, property: KProperty<*>, value: T) {
    delegate = value
  }
}

Answer 2

所以，我想我对我的问题有了一个解决方案。下面的代码将an包装在一个新类型中: Exceptional。这段代码是我想要构建的内容的起点。最终，我将拥有如下内容：

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我可以在后端服务中传递此类型的实例，并返回更精确的异常、错误或值。

interface EitherMonad<L, R> {
    val either: Either<L, R>
}

class BaseEitherMonad<L, R>(
    override val either: Either<L, R>
) : EitherMonad<L, R>

class Exceptional<R>(
    private val delegate: EitherMonad<Exception, R>
) : EitherMonad<Exception, R> by delegate {}

fun main() {

    val delegateRight = BaseEitherMonad<Exception, String>(Either.Right("howdy"))
    val exceptionalRight = Exceptional(delegateRight)
    println("IsLeft(): ${exceptionalRight.either.isLeft()}")
    println("IsRight(): ${exceptionalRight.either.isRight()}")
    exceptionalRight.either.fold({ throw it }, { println("Right: $it") })
    exceptionalRight.either.map { println(it) }

    val delegateLeft = BaseEitherMonad<Exception, String>(Either.Left(IllegalStateException("Boom!")))
    val exceptionalLeft = Exceptional(delegateLeft)
    println("IsLeft(): ${exceptionalLeft.either.isLeft()}")
    println("IsRight(): ${exceptionalLeft.either.isRight()}")
    exceptionalLeft.either.fold({ throw it }, { println("Right: $it") })
    exceptionalLeft.either.map { println(it) }
}

一次跑步：

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