ApiSample.kt

import retrofit2.GsonConverterFactory
import retrofit2.Retrofit
import retrofit2.RxJavaCallAdapterFactory
import retrofit2.http.GET
import rx.Observable
import rx.Scheduler
import rx.android.schedulers.AndroidSchedulers
import rx.schedulers.Schedulers
import java.util.concurrent.TimeUnit

class ApiSample() {

    data class Item(val id: String, val title: String)

    interface ItemService {
        @GET("/api/v2/items")
        fun items(): Observable<List<Item>>
    }

    fun api() {
        val retrofit = Retrofit.Builder()
                                .baseUrl("http://qiita.com")
                                .addConverterFactory(GsonConverterFactory.create())
                                .addCallAdapterFactory(RxJavaCallAdapterFactory.create())
                                .build();
        val service = retrofit.create(ItemService::class.java)

        service.items().subscribe { it.map { println(it.title) } }
    }
}