Expose.kt

// JVM Delegate to expose a private field, and bypass any Kotlin getters & setters
// This is a horrible abuse of reflection and should never be used, unless you absolutely have to have it.

import java.lang.reflect.Field
import kotlin.reflect.KProperty

class ExposeDelegate<T> {
    private fun field(thisRef: Any?, property: KProperty<*>): Field? {
        if (thisRef == null) return null
        val name = property.name
        val field = thisRef::class.java.getDeclaredField(name)
        field.isAccessible = true
        return field
    }

    operator fun getValue(thisRef: Any?, property: KProperty<*>): T? {
        return field(thisRef, property)?.get(thisRef) as T?
    }

    operator fun setValue(thisRef: Any?, property: KProperty<*>, value: T?) {
        field(thisRef, property)?.set(thisRef, value)
    }
}

// convenience method for readbility
fun <T> expose() = ExposeDelegate<T>()

// Useage Example -------------------------------------------------------------------------------------------------------

data class FooBar(private val value: String)

var FooBar.value by expose<String>()
fun main() {
    val fooBar = FooBar("Hello")
    println(fooBar)
    fooBar.value = "Hello World"
    println(fooBar)
}