How can I retrieve an item from a list and add it if it does not exist and get its reference again? ...

# android

[Ahmed Sellami]

How can I retrieve an item from a list and add it if it does not exist and get its reference again? I guess I can do better than this.

var playedPodcast = playedPodcasts.find {
    it.id == itemToPlay?.id
}
if (playedPodcast == null) {
    playedPodcasts.add(PlayedPodcast(itemToPlay?.id, mutableListOf()))
}
playedPodcast = playedPodcasts.find {
    it.id == itemToPlay?.id
}!!

[Christian Würthenr]

You are basically building a map...if you use a map for playedPodcasts you can do

val playedPodcasts = mutableMapOf<String, Podcast>(...)

val playedPodcast = playedPodcasts.getOrPut(itemToPlay.id) {
   PlayedPodcast(itemToPlay?.id, mutableListOf())
}

[Christian Würthenr]

If you get a list from e.g. your backend you can do

val playedPodcasts = listFromBackend.associate { podcast -> podcast.id to podcast }.toMutableMap()

[Ahmed Sellami]

Nice! But, is there a getOrPut list version? Something like getOrAdd?

[Ahmed Sellami]

That's because I have the same logic with a segments list in Podcast. Should I convert to map everytime I want to achieve this with a list?

[Christian Würthenr]

You can use getOrElse on lists, but it wont add the value to the list. Your use case is just not suited for a list 😄 If you convert to a map every time you won't have the item in the map as well as you get a new map each time. Also might come with some performance impact

[Christian Würthenr]

So ideally: Convert once to a map and then work on the map

[Ahmed Sellami]

I see, thanks.

[Daniel Dawson]

You creating a reference when you add to played podcasts. Just save it in a variable and use it directly.