Hello ! I'm in need of advice. I'm trying to get a list of chapters from webfictions. When I'm sending a list of IDs (part of URL for retrofit to dl the chapter), it is an ordered list. I want to be able to download all chapters asynchronously (in case some download faster than others), but still keep the order from the first list (first in the chapterIds list will be the first in the return List<Chapter>, etc...). Is it the proper way to do this, or I'm going at it completely the wrong way?

suspend fun getChapters(chapterIds: List<String>): List<Chapter> =
    mutableListOf<Chapter>().apply {
        chapterIds.forEach { launch { add(getChapter(it)) } }
    }

suspend fun getChapter(chapterId: String): Chapter {
    val response = service.getChapter(chapterId)
    return if (response.isSuccessful) {
        val doc = Jsoup.parse(response.body()?.string())
        Chapter(
            doc.select(CHAPTER_TITLE_QUERY).text(),
            doc.select(CHAPTER_CONTENT_QUERY).html().lines()
       )
    } else Chapter()
}

You are accessing the list asynchronously here. Instead, do something like this:

suspend fun getChapters(chapterIds: List<String>): List<Deferred<Chapter>> = coroutineScope {
    chapterIds.map { 
        async { getChapter(it) } 
    }

}

Oh nice. I will do that ! I can even do the

map,async

, and then the map.await() to return the list. That way, the person using my library won't have to do it himself. Thank you so much for the help !

Yes, it doesn't allow your app to use completed downloads though until all downloads completed. Moreover, failure of one download will cause all others to be lost. You can wrap

await

in a try/catch and make the chapters perhaps nullable, or use

mapNotNull

. Failures may also cancel the coroutine and its parents, to avoid this use

supervisorScope

instead of

coroutineScope

Thanks for the warnings @Dico! I'll keep that in mind and check how to implement a correct error management.