This class is an extension to facilitate the use of Retrofit callback responses .

RetrofitExt.kt

import retrofit2.Call
import retrofit2.Callback
import retrofit2.Response

fun <T> Call<T>.execute(success: (response: Response<T>) -> Unit,
                        failure: (t: Throwable) -> Unit) {

    enqueue(object : Callback<T> {
        override fun onResponse(call: Call<T>?, response: Response<T>) = success(response)

        override fun onFailure(call: Call<T>?, t: Throwable) = failure(t)
    })
}

Usage it!

        service.something().execute({ response ->
            when (response.isSuccessful) {
                true -> {
                    // SUCCESS RESPONSE 
                }
                false -> {
                     // SUCCESS RESPONSE WITH AN ERROR
                }
            }
        }, { throwable -> throwable.printStackTrace() })