How to use `reified` in a function that, when usi...

# getting-started

[marlonlom]

How to use reified in a function that, when using a generic function, shows a compiler error message?
The compile error message:

Cannot use 'T' as reified type parameter. Use a class instead.

[Joffrey]

Could you please share the code the gives this error?

[marlonlom]

@Joffrey hi, this is the code:

import com.beust.klaxon.Klaxon
import okhttp3.ResponseBody
import retrofit2.Converter

class KlaxonResponseBodyConverter<T> constructor(
  private val klaxon: Klaxon
) : Converter<ResponseBody, T> {

  override fun convert(value: ResponseBody): T? {
    var response: T? = null
    response = klaxon.parse<T>(value.byteStream()) // Cannot use 'T' as reified type parameter. Use a class instead.
    return response
  }

}

[Joffrey]

The problem in this case is that in the convert function, T is not reified, T is a regular generic type parameter of the class itself. Therefore, the actual T to use is not known at compile time in convert. That's why you cannot call a function like Klaxon.parse that uses a reified type parameter, because it is supposed to know from the call site at compile time what type it is.

Now, T is also erased at runtime so you can't access it anymore at that point either. What you would need is to pass the KClass itself when constructing KlaxonResponseBodyConverter , store it as a property, and use another mechanism of Klaxon that takes a KClass as input. I don't know Klaxon much, but it seems you could use klaxon.parser(theKClass).parse(StringReader(json)) or something like that. There might be more convenient alternatives, though, I really didn't search thoroughly.

[marlonlom]

@Joffrey thanks, i'll check and fix the converter, would be fine if i mention that thing of the reified and the convert function in retrofit repos, but for now i must continue with the converter 🙂