W3cubDocs

/Kotlin

notNull

Platform and version requirements: JVM (1.0), JS (1.0), Native (1.0)
fun <T : Any> notNull(): ReadWriteProperty<Any?, T>

Returns a property delegate for a read/write property with a non-null value that is initialized not during object construction time but at a later time. Trying to read the property before the initial value has been assigned results in an exception.

import kotlin.properties.Delegates

import kotlin.test.*

fun main(args: Array<String>) {
//sampleStart
var max: Int by Delegates.notNull()

// println(max) // will fail with IllegalStateException

max = 10
println(max) // 10
//sampleEnd
}

© 2010–2019 JetBrains s.r.o.
Licensed under the Apache License, Version 2.0.
https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.properties/-delegates/not-null.html