How to create a call adapter for suspending functions in Retrofit?

Question

I need to create a retrofit call adapter which can handle such network calls:

@GET(\"user\")
suspend fun getUser(): MyResponseWrapper
         


        

Answer 1

When you use Retrofit 2.6.0 with coroutines you don't need a wrapper anymore. It should look like below:

@GET("user")
suspend fun getUser(): User

You don't need MyResponseWrapper anymore, and when you call it, it should look like

runBlocking {
   val user: User = service.getUser()
}

To get the retrofit Response you can do the following:

@GET("user")
suspend fun getUser(): Response

You also don't need the MyWrapperAdapterFactory or the MyWrapperAdapter.

Hope this answered your question!

Edit CommonsWare@ has also mentioned this in the comments above

Edit Handling error could be as follow:

sealed class ApiResponse {
    companion object {
        fun  create(response: Response): ApiResponse {
            return if(response.isSuccessful) {
                val body = response.body()
                // Empty body
                if (body == null || response.code() == 204) {
                    ApiSuccessEmptyResponse()
                } else {
                    ApiSuccessResponse(body)
                }
            } else {
                val msg = response.errorBody()?.string()
                val errorMessage = if(msg.isNullOrEmpty()) {
                    response.message()
                } else {
                    msg
                }
                ApiErrorResponse(errorMessage ?: "Unknown error")
            }
        }
    }
}

class ApiSuccessResponse(val data: T): ApiResponse()
class ApiSuccessEmptyResponse: ApiResponse()
class ApiErrorResponse(val errorMessage: String): ApiResponse()

Where you just need to call create with the response as ApiResponse.create(response) and it should return correct type. A more advanced scenario could be added here as well, by parsing the error if it is not just a plain string.