Changes.kt

interface Changeable

infix fun <TTarget : Changeable, TProperty> Changeable.withChanged(change: Pair<kotlin.reflect.KProperty1<TTarget, TProperty>, TProperty>): Changeable =
    this.also {
        val (property, newValue) = change
        val field = it::class.java.getDeclaredField(property.name)
        field.isAccessible = true
        field.set(it, newValue)
    }

fun <TTarget : Changeable> Changeable.withChanged(vararg changes: Pair<kotlin.reflect.KProperty1<TTarget, Any>, Any>): Changeable =
    this.also { for (change in changes) it.withChanged(change) }

fun <TTarget : Changeable> Changeable.withChanged(changes: Iterable<Pair<kotlin.reflect.KProperty1<TTarget, Any>, Any>>): Changeable =
    this.also { for (change in changes) it.withChanged(change) }

Main.kt

fun main() {
    val p = Person("Mike", 38, 15.0)
    println(p)

    p withChanged (Person::age to 99)
    println(p)

    p.withChanged((Person::age to 999), (Person::name to "ABC"))
    println(p)


    val changes = arrayListOf<Pair<kotlin.reflect.KProperty1<Person, Any>, Any>>((Person::age to 9999), (Person::name to "DDDDD"))
    p.withChanged(changes)

    println(p)
}
data class Person(val name: String, val age: Int, val salary: Double) : Changeable