kotlin-stdlib/kotlin/require

require

inline fun require(value: Boolean)(source)

Throws an IllegalArgumentException if the value is false.

Since Kotlin

1.0

Samples

import kotlin.test.*

fun main() { 
   //sampleStart 
   fun getIndices(count: Int): List<Int> {
    require(count >= 0) { "Count must be non-negative, was $count" }
    // ...
    return List(count) { it + 1 }
}

// getIndices(-1) // will fail with IllegalArgumentException

println(getIndices(3)) // [1, 2, 3] 
   //sampleEnd
}
inline fun require(value: Boolean, lazyMessage: () -> Any)(source)

Throws an IllegalArgumentException with the result of calling lazyMessage if the value is false.

Since Kotlin

1.0

Samples

import kotlin.test.*

fun main() { 
   //sampleStart 
   fun getIndices(count: Int): List<Int> {
    require(count >= 0) { "Count must be non-negative, was $count" }
    // ...
    return List(count) { it + 1 }
}

// getIndices(-1) // will fail with IllegalArgumentException

println(getIndices(3)) // [1, 2, 3] 
   //sampleEnd
}