Cache Control Sample

CacheControlSample.kt

import retrofit2.GsonConverterFactory
import retrofit2.Retrofit
import retrofit2.RxJavaCallAdapterFactory
import retrofit2.http.GET
import rx.Observable

class CacheControlSample {

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

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

    interface ItemDataStore {
        fun items(): Observable<List<Item>>
    }

    // Singleton Class
    object ItemCache : ItemDataStore {

        var itemList = listOf<Item>()

        override fun items(): Observable<List<Item>> {
            return Observable.just(itemList);
        }

        fun reset(newItemList: List<Item>) {
            itemList = newItemList
        }

        fun isCached(): Boolean {
            return itemList.size > 0
        }
    }

    class ItemApi(cache: ItemCache) : ItemDataStore {

        val cache = cache

        override fun items(): Observable<List<Item>> {
            val retrofit = Retrofit.Builder()
                    .baseUrl("http://qiita.com")
                    .addConverterFactory(GsonConverterFactory.create())
                    .addCallAdapterFactory(RxJavaCallAdapterFactory.create())
                    .build();
            val service = retrofit.create(ItemService::class.java)

            return service.items().doOnNext { cache.reset(it) }
        }
    }

    class ItemStoreFactory {

        val cache = ItemCache

        fun create(): ItemDataStore {
            if (cache.isCached()) {
                return cache
            }

            return ItemApi(cache)
        }
    }
}