Kotlin Programming: The Big Nerd Ranch Guide, First Edition

For the More Curious: Kotlin’s Lambdas Are Closures

In Kotlin, an anonymous function can modify and reference variables defined outside of its scope. This means that an anonymous function has a reference to the variables defined in the scope where it is itself created – as in the case of the configureGreetingFunction function you saw earlier.

As a demonstration of this property of anonymous functions, update the runSimulation function to call the function returned from configureGreetingFunction multiple times:

Listing 5.14  Calling println twice in runSimulation (SimVillage.kt)

...

fun runSimulation() {
    val greetingFunction = configureGreetingFunction()
    println(greetingFunction("Guyal"))
    println(greetingFunction("Guyal")) } ...