Kotlin: Iterate over components of object

Question

Each data class object has a component for each property like component1, component2, etc.. I was wondering if there is any way in Kotlin to iterate over each component of a class. Say I have class:

data class User(age:Int, name:String) 

Could I do something like:

for(component in aUserObject){     //do some stuff with age or name } 

?

Answer 1

First of all, the componentN properties are available only on data classes, not on every object.

There is no API specifically for iterating over the components, but you can use the Kotlin reflection to iterate over properties of any class:

class User(val age: Int, val name: String)  fun main(args: Array<String>) {     val user = User(25, "Bob")     for (prop in User::class.memberProperties) {         println("${prop.name} = ${prop.get(user)}")     }   } 

Answer 2

also, you can use Properties Delegation with built-in delegate 'by map'. it's very useful for some simple stat classes.

class DbUsingStat {   private val map = mutableMapOf(     "removed" to 0,     "updated" to 0,     "skipped" to 0   )    var removed by map   var updated by map   var skipped by map    fun asMap() : Map<String, Int> = map.toMap() }  ... ...   val someStatistic = DbUsingStat().apply {   skipped = 5   removed = 10   updated = 1505 }  for((k, v) in someStatistic.asMap())   println("$k: $v")