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Using Kotlin Destructuring Declarations to Unpack a Pair or Triple

Kotlin, Destructuring Declarations, Android Development2 min read

Have you ever come across a situation where you needed to work with pairs or triples in Kotlin and found yourself manually extracting the individual values? Kotlin provides a powerful feature called "Destructuring Declarations" that allows you to easily unpack the values of a Pair or Triple into separate variables. This not only simplifies your code but also improves its readability. In this article, we will explore how to use Kotlin destructuring declarations effectively.

Unpacking a Pair

Let's start with an example of unpacking a Pair. Assume you have a function that returns a Pair of values representing coordinates, and you want to access the individual x and y coordinates separately. Here's how you can achieve it using destructuring declarations:

1fun getCoordinates(): Pair<Int, Int> {
2 // Simulating retrieval of coordinates
3 return Pair(10, 20)
6fun main() {
7 val (x, y) = getCoordinates()
8 println("x: $x, y: $y")

In the code snippet above, getCoordinates() returns a Pair of integers. By using destructuring declarations in val (x, y), we are directly assigning the values of the Pair to the variables x and y. Now we can access x and y individually without explicitly calling the first and second properties of the Pair.

Unpacking a Triple

Similarly, if you have a Triple, you can unpack its values using destructuring declarations. Let's consider an example where a function returns a Triple of values representing RGB color components:

1fun getRGB(): Triple<Int, Int, Int> {
2 // Simulating retrieval of RGB values
3 return Triple(255, 128, 0)
6fun main() {
7 val (red, green, blue) = getRGB()
8 println("Red: $red, Green: $green, Blue: $blue")

In this example, getRGB() returns a Triple of integers. By destructuring the Triple using val (red, green, blue), we can directly access the individual color components as separate variables. This makes the code more concise and easier to understand.

Ignoring Unused Values

There might be cases where you only need to extract certain values and ignore the rest. Kotlin allows you to use an underscore (_) as a placeholder for the values you don't need. Let's modify the previous example to ignore the green component:

1fun main() {
2 val (red, _, blue) = getRGB()
3 println("Red: $red, Blue: $blue")

By using _ in the destructuring declaration, we indicate that we don't need the green component. This helps to focus on the values we are interested in and reduces noise in the code.

Custom Objects and Data Classes

Destructuring declarations can also be used with custom objects and data classes by implementing the component1(), component2(), etc., functions. These functions define how the object's properties should be unpacked. Let's look at an example with a custom Person class:

1class Person(val name: String, val age: Int) {
2 operator fun component1() = name
3 operator fun component2() = age
6fun getPerson(): Person {
7 // Simulating retrieval of a Person object
8 return Person("Alice", 25)
11fun main() {
12 val (name, age) = getPerson()
13 println("Name: $name, Age: $age")

In this case, we have a Person class with name and age properties. By implementing the component1() and component2() functions, we define how the object should be destructured. Now we can directly extract the name and age using destructuring declarations.


Kotlin's destructuring declarations offer a concise and elegant way to unpack the values of Pairs, Triples, and custom objects. By leveraging this feature, you can improve the readability of your code and avoid manual extraction of individual values. Whether you're working with coordinate pairs, color components, or your own custom classes, give destructuring declarations a spin to simplify your code and make it more expressive!