Hi, if we have a method on a abstract class, like...

# announcements

[GarouDan]

Hi,

if we have a method on a abstract class, like this:

abstract fun test() : String

can we, using somehow the new kotlin techniques to change the returning value of the function in the other abstract class which extend the first one, something like this?

fun test(): String {
    return test().toString()
}

fun test(): Int {
}

The goal would be use to reuse the same name.
Maybe something using the by keyword somehow? Composing the objects (where the problem here is that I have two abstract classes)

[Shawn]

No, you’d be breaking the contract specified by the class you’re inheriting from

[Shawn]

and I’m pretty sure there isn’t any sane way to overload a no-arg method

[Shawn]

if your real test method can take different parameters than specified in the parent class then sure, there’s nothing stopping you. Otherwise, no, what you’ve described is not possible

[Diego Almeida de Oliveira]

You could use generics

[karelpeeters]

Generics don't help either I think?

[Diego Almeida de Oliveira]

You are right. The thing is, it's not possible to have two functions in the same class with same signature. And the return type doesn't define the signature, meaning that both test functions have same signature,

[GarouDan]

It looks like we can if the second type inherits from the first one, like this:

Untitled.kt

[Alowaniak]

Yea that's covariant return type
It's legal because a subtype (should) honors the same contract as it's super type

[Stephan Schroeder]

That (via the covariant keyword) is actually something that Dart has but Kotlin doesn’t https://dart.dev/guides/language/sound-problems#the-covariant-keyword