Is it possible to make a companion object equal to...

# announcements

[zceejkr]

Is it possible to make a companion object equal to the output of some function? I am trying to do something like companion object : SomeType = someFunc(). Or do you always have to declare the companion, as in companion object : SomeType {body}?

[devbridie]

companion object { val thing = someFunc() } is the closest you can get

[zceejkr]

So the problem I have is I have a generic type Decoder<A>, and I want to make the companion object of “decodable” data classes (A) an instance of Decoder<A>. I also have combinators for making these decoders, so for more complex data classes I want to construct the Decoder instance by using the combinators and the Decoders of the simpler data classes. Is there a nice way of doing this?

[marstran]

Maybe companion object : SomeType by someFunc() works?

[wbertan]

You can do something like:

typealias SomeType = () -> String

fun someFunc(): String = "asas"

object Asas : SomeType by ::someFunc

class ExampleUnitTest {
    @Test
    fun asas() {
        assertEquals("asas", Asas())
    }
}

By the way, I didn’t tested 😆

[zceejkr]

@marstran this is exactly it! many thanks

[zceejkr]

@wbertan I guess yours is the same suggestion. Thank you also!

[karelpeeters]

You can also just use an abstract class as a base class for a companion object, so delegation may not even be necessary.