Array loop

Learn to iterate over arrays with for.

Array loop

A for loop iterates over array elements in order. The for (item in array) form takes each element one by one.

val fruits = arrayOf("apple", "pear", "cherry")
for (fruit in fruits) {
    println(fruit)
}
// apple, pear, cherry

Here fruit represents one element each step. When you don't need the index, this form is the cleanest.

You don't need to write the loop variable's type; Kotlin infers it.

Exercise Print all elements

Write a fun main(). Create an array with val fruits = arrayOf("apple", "pear", "cherry"). Use for (fruit in fruits) { println(fruit) } to print all elements.

Show example solution

fun main() {
    val fruits = arrayOf("apple", "pear", "cherry")
    for (fruit in fruits) {
        println(fruit)
    }
}

Iterating by index

If you also need the index, iterate with arr.indices. The element is then taken with arr[i].

val nums = intArrayOf(3, 7, 2)
for (i in nums.indices) {
    println("$i: ${nums[i]}")
}
// 0: 3, 1: 7, 2: 2

Here both the index (i) and the element (nums[i]) are used. If you don't need the index, plain for (n in nums) is shorter.

Both forms are common; pick based on need.

Test yourself

Complete the for loop

for (____ in fruits) { println(fruit) }

Show answer

for (fruit in fruits) { println(fruit) }

What does for (fruit in fruits) { ... } do?
- Prints the indices
- Empties the array
- Takes each element in turn
- Takes only the first element
Show answer

Takes each element in turn — for-each visits each element one by one.
Match the loop forms

for (item in arr)

By element
for (i in arr.indices)

By index
arr[i]

Index access
item

Element variable

Next lesson: Array methods

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