Hey all! I'm trying to use a mutable map with integer values like so:

val myMap = mutableMapOf<Foo, Int>()

. When I try to update the map with some integer values(for e.g.

myMap[Foo] = 3

), it is giving me the following error:

Required

Int.Companion

but found

Int

Why am I getting this error and how can I resolve it?

that's bizarre. you aren't like, importing Int.Companion or anything?

you aren't like, importing Int.Companion or anything?

Nope

does

val myMap = mapOf(Foo to 3)

work?

does 

val myMap = mapOf(Foo to 3)

 work?

It does not allow me to update the map as it is immutable

well you could just say

mutableMapOf(Foo to 3)

whoops, misunderstood what you were asking

if you tell IntelliJ to "specify type explicitly", is it still <Foo, Int>?

checking..

Int

doesn't have a companion class because it's Java

if you tell IntelliJ to "specify type explicitly", is it still <Foo, Int>?

Nope, it gives me the same error. Required

Int.Companion

found

Int

I'm not clear on exactly what you want -- do you want

Int

or actual int literals/instances

I want to map my enum values to int literals/instances

okay, so

val map = mutableMapOf<MyEnum, Int>()
map[MyEnum.WHATEVER] = 3

should definitely work

Alright, this works. I was previously using:

val map = mutableMapOf(
    MyEnum.INSTANCE1 to Int,
    MyEnum.INSTANCE2 to Int,
    MyEnum.INSTANCE3 to Int
)

why does it fail in this case?

because when you use a class (i.e.

Int

) as a value (i.e. as an expression, like you are here), it automatically replaces it with the companion object, i.e.

Int.Companion

, which doesn't exist because

Int

is actually an alias for java.lang.Integer (kind of), which being Java doesn't have a

Companion

object

yep, it worked when I replaced

Int

with

0

in the aforementioned code

yeah, it's a singleton instance

Thanks Max!

Harry, it doesn’t work because when you declare

MyEnum.INSTANCE1 to Int

you’re creating a

Pair<MyEnum, Int.Commpanion>

but when executing

myMap[INSTANCE1] = 3

you’re trying to assign an

Int

to that Entry, so the value type mismatches and the compiler tells you. You were simply trying the wrong thing, what you wanted were int literals, as you found out in this thread. Please read about companion objects here: https://kotlinlang.org/docs/reference/object-declarations.html#companion-objects

@Matteo Mirk I stand corrected 🙂

Didn’t want to sound impolite, sorry 😄