ItemKeyedSubredditDataSource.kt

/**
 * A data source that uses the "name" field of posts as the key for next/prev pages.
 */
class ItemKeyedSubredditDataSource : ItemKeyedDataSource<String, RedditPost>() {

    override fun loadInitial(params: LoadInitialParams<String>,
                             callback: LoadInitialCallback<RedditPost>) {

        val request = redditApi.getTop(
                subreddit = subredditName,
                limit = params.requestedLoadSize)

        // Retrofit Call onResponse omitted
        
        callback.onResult(items)
    }

    override fun loadAfter(params: LoadParams<String>,
                           callback: LoadCallback<RedditPost>) {

        val request = redditApi.getTopAfter(
                subreddit = subredditName,
                after = params.key,
                limit = params.requestedLoadSize)

        // Retrofit Call onResponse omitted
        
        callback.onResult(items)
    }

    override fun getKey(item: RedditPost): String {
        return item.name
    }
}