Can I set a custom key (instead of element index) in `LazyColumnFor` composable?

# compose

[Julius Marozas]

Can I set a custom key (instead of element index) in LazyColumnFor composable?

[Zach Klippenstein (he/him) [MOD]]

I thought LazyColumnFor used the element itself as the key, unless that changed recently.

[Julius Marozas]

It probably has then. Here is the source.

[Julius Marozas]

So should I just copy LazyFor composable (since it's private) and use a custom key? Or is there another way?

[Zach Klippenstein (he/him) [MOD]]

What do you need a custom key for? Can you not just put the keys you want in the list?

[Julius Marozas]

I have a list of items that have unique ids. I want to avoid recomposing the entire tree under LazyColumnFor when I insert a new item at the beginning of the list. So I was hoping that I could solve this by specifying the key as the id of the item (similarly to how it is usually done in React).

[Zach Klippenstein (he/him) [MOD]]

You could do a couple things:

1. Just pass a list of IDs, and look up the actual element in a map.

2. Either change the definition of equals for your element type to only consider ID, or wrap your values in a type that does this.

Either way, I would file a feature request issue to the compose project to ask for this feature (tracked link is in channel topic/description)

[Zach Klippenstein (he/him) [MOD]]

Both of those solutions potentially require creating new lists on every composition, which isn't ideal.

[Julius Marozas]

Thanks for the suggestions! I have filed an issue.