在jetpack compose中使用非本地state？

Question

Is it Ok to use non-local state from a Composable function? An example would be a Composable that shows a Text with a String taken from a MutableState stored as a member of an object retrieved through an Ambient, like this:

data class ServiceX (
   val whateverString: MutableState<String>("meow")
)


@Composable
fun Whatever() {
   val serviceX = AmbientServiceX.current
   Text(serviceX.whateverString)
}

Will the Composable function repaint when whateverString changes? Are there any problems with this?

Answer 1

It should technically work, But you'd probably want to change MutableState to mutableStateOf which does some more compose goodies under the hood.

But I'd suggest avoiding patterns like this in compose. Ambients in general should be used rarely, as ambients make composables 'magic' with it being non obvious where the value came from or where a value change was triggered. It essentially makes your code very hard to debug.

Lean on the side of creating isolated components as these are way simpler to build and maintain - and are the big benefit of compose.

@Composable
fun Whatever(whateverString: String) {
   Text(whateverString)
}