Iterator Pattern in Kotlin | Design Patterns

Iterator Pattern is a relatively simple and frequently used design pattern. There are a lot of data structures/collections available in every language. Each collection must provide an iterator that lets it iterate through its objects.

However, while doing so it should make sure that it does not expose its implementation.

package behavioral
class Novella(val name: String)
class Novellas(val novellas: MutableList<Novella> = mutableListOf()) : Iterable<Novella> {
    override fun iterator(): Iterator<Novella> = NovellasIterator(novellas)
class NovellasIterator(val novellas: MutableList<Novella> = mutableListOf(), var current: Int = 0) : Iterator<Novella> {
    override fun hasNext(): Boolean = novellas.size > current
    override fun next(): Novella {
        val novella = novellas[current]
        return novella
fun main(args: Array<String>) {
    val novellas = Novellas(mutableListOf(Novella("Test1"), Novella("Test2")))
    novellas.forEach { println( }
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