The yield Keyword in Scala Programming Language

In this article, we will learn how to use the yield keyword in Scala with the help of different examples.

The yield keyword is used with for loops. In each iteration of the for loop, yield generates a remembered value.

It acts as a buffer for the for loop. For each iteration of the for loop, items are added to this buffer.

Once the for loop finishes all its iterations, a collection of all the yielded values is returned.

The type of collection that is returned. The same type for loop was iterating, so a List yields a List, a Map yields a Map, an array yields an array, and so on.

The syntax of yield:

for() yield variable;

Using the yield Keyword in an Array in Scala

We will iterator over all the elements of an array using for loop and use the yield keyword to store elements at each iteration of the for loop.

Example code:

object MyClass {
    def main(args: Array[String]) : Unit = {
        val array = Array(100,200,300,500,600)
        
        var buffer = for (i <- array if i > 200) yield i
        
        for(i<-buffer)
        {
            
            println(i) 
        } 
    }
}

Output:

300
500
600

yield With Scala List

We will iterate over all the elements of a List using for loop and use the yield keyword to store elements at each iteration of the for loop and perform some operation on them.

object MyClass {
    def main(args: Array[String]) : Unit = {
       val myList = List(1,2,3,4,5,6,7,8,9,10)
       
       var buffer = for (i <- myList) yield i*i*i
        println("Values from yield")
            for(i <- buffer) println(i)
    }
}

Output:

Values from yield
1
8
27
64
125
216
343
512
729
1000