Is it possible to implement custom destructuring for non data class in Kotlin?

Question

In Kotlin data classes can be destructured like so:

fun main(args: Array<String>) {
    val thing = Stuff(1, "Hi", true)
    val(thing1, thing2, thing3) = thing

    println(thing1)
}

data class Stuff(val thing1: Int, val thing2: String, val thing3: Boolean)

I could be misreading the docs, or maybe I just couldn't find an example, but I'm looking for a way to implement custom destructuring of non-data classes. Is this possible in Kotlin?

Answer 1

I was able to make this work like this:

fun main(args : Array<String>) {
    val person = Person("first", "last")
    val(param1, param2) = person
    println(param1)
    println(param2)
}

class Person(val firstName: String, val lastName: String) {
    operator fun component1() = firstName
    operator fun component2() = lastName
}

Answer 2

Destructuring is performed by calling functions component1, component2, component3 etc, on the instance being destructured.

These functions can be either member functions declared inside your class or extension functions. Also component functions must have operator keyword to indicate they are to satisfy a convention, namely destructuring one.

For data classes compiler generates corresponding component function for each property of data class declared in its primary constructor.

An example of class with custom component functions:

class Result(val e: Exception?) {
    val hasFailed = e != null

    operator fun component1(): Exception? = e
    operator fun component2(): Boolean = hasFailed
}

val (e, hasFailed) = Result(RuntimeException())