Is anyone using dependency injection / oop for the...

# compose

[Scott Kruse]

Is anyone using dependency injection / oop for theming in compose? I see a lot of top level declaration in samples / material documentation

[Colton Idle]

I think themes end up being one of those cases where Composition Locals (better known as Globals IMO) make sense to use instead of having to pass them down absolutely everywhere.

[romainguy]

Well they are local to a composition. They're not true global values because of that. They're scoped globals if you prefer ^^

[jw]

With class loader hierarchies technically globals are also scoped globals

[Colton Idle]

I still don't really understand the name composition locals. Isn't any variable defined in a composable a composition local?

[adjpd]

I think they were called ambients before. At least there's a few references to them in the pathway docs. The name is confusing, yeah. I guess you can think of those values as local to a composition tree. I just think of them as scoped globals.

[adjpd]

I also use them with default function parameters as a cheap alternative to dependency injection.

[jw]

@Colton Idle a variable defined inside a @Composable is more like a recomposition local as its lifetime is tied to a single recomposition. Composition locals survive for the lifetime of the composition object across multiple recompositions

[Colton Idle]

Oooh. That's actually super helpful. Recomposition local vs composition local.

[jw]

Well... kinda. It's mostly that. You probably won't harm yourself with that mental model, but there's also more nuance since they're hierarchical and can exist at different points in the tree.

[jw]

Technically the composition owns the tree and therefore holds these composition locals, but since they can be installed at various points of the composable hierarchy installing a composition local does not mean it's visible to 100% of the composables in that composition

[jw]

A name which is fully accurate would probably be like 100 characters long and "composition local" is Close Enough™

[romainguy]

We moved away from Ambient because we deemed that term even more confusing

[Colton Idle]

Should have just gone with Context to really mess with all of us.

[adjpd]

"You only had a fuzzy idea what the context was before. But good news! You can now define your own!"

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

CompositionLocal is also meant to pattern match to ThreadLocal. Just like TLs, CLs can have different values depending on where they're read.

[Colton Idle]

Time to lookup what a ThreadLocal is. 😅