CODESAMPLE

Iterator - Kotlin

Iterator Kotlin

The Iterator pattern provides a way to access the elements of an aggregate object sequentially without exposing the underlying representation. It defines a standard interface for creating iterators, allowing clients to traverse a collection without knowing its specific implementation. This promotes loose coupling and flexibility.

In Kotlin, we leverage the built-in iterator() function available for all collections, which automatically provides an efficient and idiomatic implementation of the Iterator pattern. This example creates a simple TaskList class and uses Kotlin’s standard Iterator functionality to iterate through the tasks. The code directly utilizes for...in loops, which implicitly call the iterator() function, showcasing Kotlin’s concise and functional approach to iteration.

// TaskList.kt
data class Task(val description: String)

class TaskList {
    private val tasks = mutableListOf<Task>()

    fun addTask(task: Task) {
        tasks.add(task)
    }

    fun getTasks(): List<Task> {
        return tasks
    }

    // Kotlin's Iterable interface provides iterator() by default for List.
    // No explicit Iterator implementation needed for basic iteration.
}

fun main() {
    val taskList = TaskList()
    taskList.addTask(Task("Grocery Shopping"))
    taskList.addTask(Task("Laundry"))
    taskList.addTask(Task("Code Review"))

    println("Tasks:")
    for (task in taskList.getTasks()) {
        println("- ${task.description}")
    }

    println("\nUsing an explicit iterator:")
    val iterator = taskList.getTasks().iterator()
    while (iterator.hasNext()) {
        val task = iterator.next()
        println("- ${task.description}")
    }
}