Hello can i define a lambda that accepts a mutable variable kotlinlang #announcements

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Title

o

otakusenpai

10/10/2018, 8:16 PM

Hello, can i define a lambda that accepts a mutable variable as parameter?

d

Dico

10/10/2018, 8:17 PM

You want to be able to modify a variable that's passed into the lambda from the lambda?

o

otakusenpai

10/10/2018, 8:17 PM

yes

val bbToString = { bb: ByteBuffer, d: String -> d = String(bb.array(), Charset.forName("US-ASCII")) }

d

Dico

10/10/2018, 8:18 PM

You can't do this in Kotlin

o

otakusenpai

10/10/2018, 8:19 PM

ok then

d

Dico

10/10/2018, 8:19 PM

If you must return multiple values, you can use

Pair<>

or a data class

You can also modify any variables in the scope of the lambda, of course

o

otakusenpai

10/10/2018, 8:25 PM

ok gotcha

s

Sam

10/11/2018, 2:57 AM

@otakusenpai You could pass by reference via AtomicReference or use StringBuilder etc

val lambda = { s : AtomicReference<String> ->
    s.set( "updated string" )
}

fun main( argv : Array<String> ) {
    val string = AtomicReference<String> ("initial value")

    println( string )

    lambda( string )

    println( string )

}

Here the reference is passed by value but you are working with what is being referred to

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