coroutines3.kt

import kotlinx.coroutines.experimental.CommonPool
import kotlinx.coroutines.experimental.android.UI
import kotlinx.coroutines.experimental.launch
import kotlinx.coroutines.experimental.withContext
import retrofit2.Call
import retrofit2.Retrofit
...

class Api {
  ...
 
  fun <T> request(call: Call<T>,
              onSuccess:(T?)-> Unit,
              onFailure:(IOException)-> Unit) = launch(UI) {
      try {
          val result = withContext(CommonPool) { call.execute() }
          onSuccess(result.body())
      } catch (exception: IOException) {
          onFailure(exception)
      }
  }
}