Android Kotlin retrofit coroutine requests with moshi error

Question

i'm currently working on some basic app which i try to get an response from API - List of objects.

My data classes Are:

@JsonClass(generateAdapter = true)
data class Tag(
    @Json(name = "id")
    val id: Int,
    @Json(name = "name")
    val name: String
)

@JsonClass(generateAdapter = true)
data class Test(
    @Json(name = "count")
    val count: Int,
    @Json(name = "next")
    val next: Int,
    @Json(name = "previous")
    val previous: Int,
    @Json(name = "results")
    val results: List<Tag>
)

My retrofit build code is:

val moshi = Moshi.Builder()
    .add(KotlinJsonAdapterFactory())
    .build()

return Retrofit.Builder()
    .baseUrl(SERVER_BASE_URL)
    .addCallAdapterFactory(CoroutineCallAdapterFactory())
    .addConverterFactory(MoshiConverterFactory.create(moshi))
    .build()

And my request is very simple:

@GET("api/tags")
suspend fun getTags(): Deferred<Test>

But when i am calling getTags() i get the following error:

java.lang.IllegalArgumentException: Unable to create converter for kotlinx.coroutines.Deferred<com.example.kotlin_ex2.models.Test>
     Caused by: java.lang.IllegalArgumentException: No JsonAdapter for kotlinx.coroutines.Deferred<com.example.kotlin_ex2.models.Test> (with no annotations)

Already tried many other ways with no success, what could be the problem?

Thank you

Answer 1

It is because you are using both suspend and Deferred in one function. Convert

@GET("api/tags")
suspend fun getTags(): Deferred<Test>

to

@GET("api/tags")
fun getTags(): Deferred<Test>

Answer 2

Solved. As i can see, i just needed to remove the Deferred class and write it that way:

@GET("api/tags")
suspend fun getTags(): Test

and no need to call await() from inside the Coroutine.