Tuple. In Scala 3.3, a tuple combines 2 or more values in a single unit. For example, we can combine a string and an integer with some simple syntax.
With tuples, we build abstractions over related values. This helps simplify many parts of our Scala programs. A function can return more than 1 value in a tuple.
First example. Here we create 2 tuples, each with 2 items. The tuples have a String and Int. We can access the first and second items in them.
Detail We can access the first and second items from a tuple with the "_1" and "_2" syntax.
Note The first item in a tuple is at index 1, not index 0, and we must use "_1" to get it.
object Program {
def main(args: Array[String]): Unit = {
// Create and print two tuples.
val identity1 = ("ABC", 10)
val identity2 = ("DEF", 20)
println(identity1)
println(identity2)
// Get first and second items from a tuple.
val first = identity1._1
val second = identity1._2
println(first)
println(second)
}
}(ABC,10)
(DEF,20)
ABC
10
Return multiple values. Often in programs we want to return multiple values from a function. Parameters, classes, or tuples may be used. Here we return a tuple from function.
Note The upperName def receives a name String and returns a two-item tuple containing the uppercase name and the original name.
object Program {
// This def returns a two-item tuple.// ... It uppercases the argument String.
def upperName(name: String): (String, String) = (name.toUpperCase(), name)
def main(args: Array[String]): Unit = {
// Call upperName function with String.
val name = "scala"
val result = upperName(name)
println(result)
}
}(SCALA,scala)
Unpack. We can unpack a tuple in an assignment statement. Here the function returns a tuple with two items in it. We assign the values number1 and number2 to those items.
Tip This syntax immediately unpacks a tuple. This can make a program simpler to read.
object Program {
// Return a tuple.
def twoNumbers(x: Int): (Int, Int) = (x * 2, x * 4)
def main(args: Array[String]): Unit = {
// Unpack the tuple returned by the function.
val (number1, number2) = twoNumbers(3)
println(number1)
println(number2)
}
}6
12
Match. We can use a tuple as the argument of a match construct. We specify values within match cases to require specific values in a tuple.
Here The test() method receives a String, Int tuple. If the first item is "bird" the first case is matched.
object Program {
def test(animal: (String, Int)) = {
animal match {
case ("bird", size) =>
println("Bird weighs " + size)
case (animal, size) =>
println("Other animal " + animal + ", " + size)
}
}
def main(args: Array[String]): Unit = {
// Call test method with tuple argument.
val animal = ("bird", 20)
test(animal)
val animal2 = ("cat", 300)
test(animal2)
}
}Bird weighs 20
Other animal cat, 300
Tuple list. With a list of tuples we can make a 2D array or a collection of complex elements. Here we use 3 items in each tuple and access them in a for-loop.
object Program {
def main(args: Array[String]): Unit = {
// Create list of tuples.
val animals = List(("cat", 10, "yellow"), ("bird", 1, "blue"))
// Loop over tuples.
for (value <- animals) {
println(value._1 + " is " + value._3)
println("... weighs " + value._2)
}
}
}cat is yellow
... weighs 10
bird is blue
... weighs 1
Summary. Tuples are common in Scala. They have a simple syntax form, so we can use them with minimal effort. They combine data together, enabling manipulation of data units.
Dot Net Perls is a collection of tested code examples. Pages are continually updated to stay current, with code correctness a top priority.
Sam Allen is passionate about computer languages. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States.
This page was last updated on Dec 12, 2023 (edit).