Generic function with generic 2D array

Question

How can one implement a generic function which creates an empty generic 2D array? In the following code sample an empty 1D array is created and has the expected type. However, when I call test2D I get an error:

java.lang.ClassCastException: [[Ljava.lang.Object; cannot be cast to [[Ljava.lang.Integer;

inline fun <reified T> make1D(mask: Array<T>) : Array<T> {
  val res : Array<T> = arrayOf()
  return res
}

@Test
fun test1D() {
  val a : Array<Int> = arrayOf(0)
  val b : Array<Int> = make1D(a)
  assertEquals(0, b.size)
}

inline fun <reified T> make2D(mask: Array<Array<T>>) : Array<Array<T>> {
  val res : Array<Array<T>> = arrayOf() 
  // I expect T to be equal to Int when calling from test below, 
  // and res to have Integer[][] type;
  // however it has Object[][] type instead
  return res
}

@Test
fun test2D() {
  val a : Array<Array<Int>> = arrayOf(arrayOf(0))
  val b : Array<Array<Int>> = make2D(a)
  assertEquals(0, b.size)
}

Issue on You Track

Michele d'Amico
– Michele d'Amico

2016-01-03 12:47:05 +00:00
Commented Jan 3, 2016 at 12:47 — Michele d'Amico
– Michele d'Amico, Commented Jan 3, 2016 at 12:47

Jayson Minard · Accepted Answer · 2015-12-29 20:53:03Z

1

I think you are one level too deep for the reified parameter. Maybe it is a bug, creating a YouTrack issue will help to find out. This code works when you let T be the whole inner array:

inline fun <reified T> make2D(mask: Array<T>): Array<T> {
    val res: Array<T> = arrayOf<T>()
    return res
}

@Test
fun test2D() {
    val a: Array<Array<Int>> = arrayOf(arrayOf(0))
    val b: Array<Array<Int>> = make2D(a)
    assertEquals(0, b.size)
}

After you create a YouTrack issue, please post the issue number here for tracking.

answered Dec 29, 2015 at 20:53

Jayson Minard

86.3k40 gold badges199 silver badges233 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Generic function with generic 2D array

1 Answer 1

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related