Functional Kotlin

Immutable reference  (referential immutability)

Referential immutability enforces that, once a reference is assigned, it can't be assigned to something else. Think of having it as a val property of a custom class, or even MutableList or MutableMap; after you initialize the property, you cannot reference something else from that property, except the underlying value from the object. For example, take the following program:

class MutableObj { var value = "" override fun toString(): String { return "MutableObj(value='$value')" } } fun main(args: Array<String>) { val mutableObj:MutableObj = MutableObj()//(1) println("MutableObj $mutableObj") mutableObj.value = "Changed"//(2) println("MutableObj $mutableObj") val list = mutableListOf("a","b","c","d","e")//(3) ...