```val newState = state.copy( items = state.items...

# android-architecture

[ursus]

val newState = state.copy(
	items = state.items.map {
		if (it.id == id) {
			it.copy(
				text = newText
			)
		} else {
			it
		}
	}
)

[tschuchort]

The correct answer is to use optics/lenses and datatype generic programming (à la SYB or generics-sop in Haskell lingo). I think arrow has lenses, although they were quite annoying to use last time I checked. So it may be better to wait a few more months until arrow-meta and such stabilizes and a nicer lens API may be released.

[tschuchort]

Basically, lenses are composable copy-set methods, such that for setItem: State.(Item) -> State and setId: Item.(Id) -> Item you can compose them to a method setItemId: State.(Id) -> State .

[ursus]

what would be the syntax .. item = item.setId ?

[tschuchort]

something like that. I only know them from Haskell