hi ```fun main() { val arrayB:Array<B> =...

# getting-started

[Gamar Mustafa]

hi

fun main() {
   val arrayB:Array<B> = arrayOf(B())
   val arrayA:Array<A> = arrayB
   val arrayA2:Array<A> = arrayOf(B())

}

open class A()
class B: A()

why second line gives error but third doesnt? i know that arrays are invariant but then why it's okay with the 3rd line?

[Gleb Minaev]

Because Array is not covariant, so you cannot cast Array<B> to Array<B>. But at the same time you can cast all elements of type B to type A, which is done with every element in arrayOf(...) in the third line.

Another way to see the problem is that when you have Array<B> you cannot expose it as Array<A>, otherwise one can put element of type A in it which is prohibited. However, having a bunch (don't know how to say "collection" not referring Collection interface) of elements of type B, one can say that it is a bunch of elements of type A. That's why vararg arguments are of type Array<out E> instead of Array<E>.

[Michael Krussel]

If you replace the third line with val array:A2:Array<A> = arrayOf<B>(B()) you would get the failure, but the compiler is translating it to ``val arrayA2Array<A> = arrayOf<BA>(B())` which is allowed

[Gamar Mustafa]

so it converts every B object to A implicitly before assigning it to to the array?

[Michael Krussel]

Converts the B reference to an A reference, the object is still a B

[Gamar Mustafa]

okay, i think i got it

[Gamar Mustafa]

thanks @Gleb Minaev @Michael Krussel. much appreciated!