Saver

The Saver describes how the object of Original class can be simplified and converted into something which is Saveable.

What types can be saved is defined by SaveableStateRegistry, by default everything which can be stored in the Bundle class can be saved. The implementations can check that the provided value can be saved via SaverScope.canBeSaved

You can pass the implementations of this class as a parameter for rememberSaveable.

import androidx.compose.runtime.saveable.Saver

data class Holder(var value: Int)

// this Saver implementation converts Holder object which we don't know how to save
// to Int which we can save
val HolderSaver = Saver<Holder, Int>(save = { it.value }, restore = { Holder(it) })

Summary

fun restore(value: Saveable): Original?

fun SaverScope.save(value: Original): Saveable?