Kotlin: Programing is printing kotlin.unit

user_12907453 0
Viewed 533

My Kotlin Class will run but it prints out the words: kotlin.Unit. What do I need to change?

fun main(args: Array<String>) {
    var myDuck = Duck()
    println(myDuck.quack())
}
class Duck() {
    fun quack () {
        println("Quack, Quack, Quack")
    }
}
kotlin
4 Answers

It is printing that because you are printing the return type of a function that does not return any value. If you are familiar with other languages it is the same as having a void return type.

In kotlin a funtion without a return type returns a unit type, and so when you print the return value of Duck::quack you are printing the string value of a Unit value.

The simplest solution is to not print the return value of Duck::quack; however, if you would like the prinlt to print the return of Duck::quak, it needs to return a useful value. For examle:

class Duck() {
    fun quack(): String {
        return "Quack, Quack, Quack"
    }
}

fun main(args: Array<String>) {
    var myDuck = Duck()

    println(myDuck.quack())
}

or more idiomatically:

class Duck() {
    val quack: String = "Quack, Quack. Quack"
}

fun main(args: Array<String>) {
    var myDuck = Duck()

    println(myDuck.quack)
}
user_115480570

It's anought to call

    myDuck.quack()

wich has already println inside. Calling println(myDuck.quack()) prints type of myDuck.quack because it doesn't return any value.

user_134151640

1.prints "kotlin.Unit" if you don't specify the type

fun main(args: Array<String>) {
    var myDuck = Duck()
    println(myDuck.quack())
}
class Duck():String {
    fun quack () {
        return "Quack, Quack, Quack"
    }
}
user_96984970

Also as shortly:

fun main() {        
        println(Duck.quack())
    }

class Duck() {
    fun quack () = "Quack, Quack, Quack"
    }
user_92349300
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