Kotlin: an array of generics

Question

I am writing a B-tree that can have many keys in one node and I am facing a problem. When I create the Ints array , everything works fine:

class Node<K: Comparable<K>> (val t: Int) {
    val keys: Array<Int?> = Array<Int?> (t*2-1, {null})
}

But I want to create a Generics Ks array :

class Node<K: Comparable<K>> (val t: Int) {
    val keys : Array<K?> = Array<K?> (t*2-1, {null})
}

In this case, the compiler issues this error message:

'Kotlin: Cannot use 'K' as reified type parameter. Use a class instead.'

Question: How do I create a Generics array?

UPD: thanks for all the answers! MutableList seems to be a good solution for my purpose.

+3

Anton Ostrouhhov 29 Mar 17 at 12:26

1 answer

Adel Nizamutdinov · Accepted Answer · 2017-03-29T15:53:24+0000

You can use instead List<K>

, it doesn't require types reified

.

To use shared parameters with Array<K>

you need a shared parameter reified

(so you can get its class)

You cannot use reified

with classes, only with functions, and functions must beinline

So I suggest you use it class

as late as possible, with specific or non- reified

typed types.

Meanwhile, you can use functions like these

inline fun <reified K : Comparable<K>> computeKeys(t: Int): Array<K?> =
    Array(t * 2 - 1) { null }