Hi, is it possible to have a default value for a generic type of a class ? Like that code in TypeScr...

# getting-started

[Ayfri]

Hi, is it possible to have a default value for a generic type of a class ?
Like that code in TypeScript :

class Test<T = string> {
    readonly thing: T
}

const a = new Test() // this works
const b = new Test<number>() // this too

[Nathan Bedell]

Hi, unfortunately it looks like this hasn't been implemented yet. I'd love to see something like this feature though!

[James Whitehead]

If you are saying T can be a subclass of String you could do

class Test<T : String> {}

[Dave K]

It looks like they’re wanting to omit the <> entirely and have the default implication be that it’s a string, but also support other things explicitly such as Number

[Dave K]

Could you not do

fun Test() = Test<String>()

[Dave K]

with constructor arg or not https://pl.kotl.in/mJLv3yyUg

Though with the lateinit var has to have a non nullable value and also isn’t read only. However since the example didn’t have a constructor argument I wasn’t sure what the intended use was

[Dave K]

If you’re using a constructor argument then the type may not even be necessary to specify explicitly https://pl.kotl.in/pfl7VDG97

[Ayfri]

This is nice thanks !
Also is there a workaround for interfaces (with also a generic type an some properties that have that type) ?

[diesieben07]

Typealiases can do this:

class Test<T> { }
typealias DefaultTest = Test<String>

Not an ideal solution but the closest you can get until we have native support for this in the language.