What’s the most idiomatic way to attach a reified ...

# codereview

[arve]

What’s the most idiomatic way to attach a reified function to an interface?

currently I’m adding an extension function next to the interface in the same file, but it’s not very discoverable: The user has to know about this and import it explicitly before use:

interface IExample {
  fun <T> something(cls: KClass<T>)
}

inline fun <reified T> ITest.something() = something(T::class)

val t: IExample = Example()
// caller has to manually know about, and import extension function before they can do
t.something<String>()

[Joffrey]

That's what I usually do as well. To be honest, this specific issue with discoverability is common enough across many libraries that I personally rely a lot on the tooling to give me all the overloads (I always use Ctrl+Space to autocomplete members in IJ and it finds and auto-imports extensions when needed), so I don't consider this much of a problem anymore.

[arve]

alright, thanks. I have (thought i had) noticed some times it isn’t discovered automatically but maybe i have just been impatient or some misconfiguration.

[Joffrey]

I haven't faced those in a while, but maybe it's just my memory playing games 😄

[Klitos Kyriacou]

The way you've done it is exactly how Jackson defines its Kotlin extensions:

inline fun <reified T> ObjectMapper.readValue(content: String): T = readValue(content, jacksonTypeRef<T>())

And indeed, whenever I try to use the readValue extension, I have trouble getting IntelliJ IDEA to recognize it until I manually import com.fasterxml.jackson.module.kotlin.readValue.

[Joffrey]

@Klitos Kyriacou did you try Ctrl+Space for completing these functions? It consistently works for me, I just have to pick the reified extension from the list instead of the regular member. (Don't get me wrong, I'm not saying it's perfect, but I got used to working like that and it doesn't feel too much of a hassle for me)

[Klitos Kyriacou]

Ah, yes indeed it does. I thought Ctrl+Space only listed the member function variants, but in fact it does list the extension functions, but only at the bottom of a very long list that requires scrolling down twice, so I didn't see them. Thanks for pointing this out, as it is definitely a better experience than having to import manually.

[loke]

@arve Completion is very broken when using K2, so if you're using that, you may want to switch back to K1 until they fixed it.