CODEWITHSUNDEEP
kotlinmoshi
Hung Nguyen
Hung Nguyen

Reputation: 1156

No JsonAdapter for Generic Type (inside generic function)

I am facing an error No JsonAdapter for R when parsing JSON to data class inside a generic function, I researched and tried many ways but it is still not working. The problem is that generic function doesn't know what is actually the type of generic parameter R so I can't manually assign the type of R when parsing.

How can I resolve this problem? :(

fun <T, R> sendRequest(msg: Deribit.Request.Message<T>): Deribit.Response.Result<R> {
    ...
        val type = object : TypeToken<Deribit.Response.Result<R>>() {}.type

        return moshi.adapter<Deribit.Response.Result<R>>(
            type
        ).fromJson(jsonElement.toString())
    ...
}

I also use reified function that return ParameterizedTypeReference but it still not working

private inline fun <reified T: Any> typeRef(): ParameterizedTypeReference<T> = object: ParameterizedTypeReference<T>(){}
...
// USAGE
val data = moshi.adapter<Deribit.Response.Result<R>>(
            typeRef<Deribit.Response.Result<R>>().type
        ).fromJson(jsonElement.toString())

Thank you and best regards!!!

Upvotes: 0

Views: 1166

Answers (1)

Alexey Romanov
Alexey Romanov

Reputation: 170815

Making it

inline fun <reified T, reified R> sendRequest...

should work. Alternately, pass the type you need or enough to construct it as an argument. E.g.

fun <T, R> sendRequest(msg: Deribit.Request.Message<T>, clazzR: Class<R>): Deribit.Response.Result<R> {
    // Type object for Result<R>
    val type = Types.newParameterizedType(Deribit.Response.Result::class.java, clazzR)
    ...
}

Upvotes: 1

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