15-destructuring.kt

package org.athenian

import kotlin.random.Random

// See https://proandroiddev.com/kotlin-destructuring-declarations-46aad0ee5261

fun main() {

  data class Person(val name: String, val age: Int)

  class Location(val latitude: Double, val longitude: Double) {
    operator fun component1() = latitude
    operator fun component2() = longitude
    operator fun component3() = "A string using $latitude and $longitude"
  }

  class RandomVals {
    val randomVal1: Int
      get() = Random.nextInt()

    val randomVal2: Int
      get() = Random.nextInt()
  }

  operator fun RandomVals.component1() = randomVal1
  operator fun RandomVals.component2() = randomVal2
  operator fun RandomVals.component3() = randomVal1 + randomVal2

  // Kotlin data classes include destructuring calls automatically
  val person = Person("Thomas", 40)
  val (name, age) = person
  println("$name is $age years old")

  // Regular classes can add destructuring support by overloading the componentN operators
  val loc = Location(38.2, 110.8)
  val (lat, long, desc) = loc
  println("Lat/Long = $lat/$long $desc")

  // You can add destructuring support to existing classes with extension functions
  val randomVal = RandomVals()
  val (val1, val2, sum) = randomVal
  println("val1, val2, sum = $val1 and $val2 and $sum")

  // You can use destructured assignments in loops as well
  for ((v1, v2, s) in List(5) { RandomVals() })
    println("v1, v2, s = $v1 and $v2 and $s")
}