Tuples in Scala

Tuples

Tuple is a value that contains a fixed number of elements, each with a distinct type. Tuples are immutable. Tuples are especially handy for returning multiple values from a method or function.

A tuple with two elements can be created as follows:

val ingredient = ("Sugar" , 25)

val t = new Tuple3(1, "hello", Console)

To represent tuples, Scala uses a series of classes: Tuple2, Tuple3, etc., through Tuple22. Each class has as many type parameters as it has elements.

Accessing the elements

One way of accessing tuple elements is by position. The individual elements are named _1, _2, and so forth.

println(ingredient._1) // Sugar

println(ingredient._2) // 25

Pattern matching on tuples

A tuple can also be taken apart using pattern matching:

val (name, quantity) = ingredient

println(name) // Sugar

println(quantity) // 25

Another example of pattern-matching a tuple:

val planets = List(("Mercury", 57.9), ("Venus", 108.2), ("Earth", 149.6),("Mars", 227.9), ("Jupiter", 778.3))

planets.foreach{

  case ("Earth", distance) =>  println(s"Our planet is $distance million kilometers from the sun")

  case _ =>

}

Iterate over the Tuple

We use Tuple.productIterator() method to iterate over all the elements of a Tuple.

Example

val t = (4,3,2,1)

t.productIterator.foreach{ i =>println("Value = " + i )}

//Output

Value = 4

Value = 3

Value = 2

Value = 1

Creating a tuple with ->

Another cool feature, you can create a tuple using this syntax:

1 -> "a"

This creates a Tuple2(1,a)

Tuples swap method

Example:

val t = Tuple2("Scala", "hello")

println("Swapped Tuple: " + t.swap )

//Output

Swapped Tuple: (hello,Scala)

t: (String, String) = (Scala,hello)

Note: swap operation performed on only those tuples whose element count is 2 only. If element count is more than 2 it will give you error

Example:

val t = Tuple3("Scala", "hello","Sarvana")

println("Swapped Tuple: " + t.swap )

//Output

error: value swap is not a member of (String, String, String)

println("Swapped Tuple: " + t.swap )

Converting Tuple to String in Scala

We can use tuple.toString() method to concatenate elements of tuple to string.

val t = (1, "hello",20.2356)

val strVal = t.toString()

println("Concatenated String: " + strVal)

//Output

Concatenated String: (1,hello,20.2356)

t: (Int, String, Double) = (1,hello,20.2356)

strVal: String = (1,hello,20.2356)