aego/modules/savegame/res/docs/persistence.md

id, try, try_select, icon, group, title, order

id	try	try_select	icon	group	title	order
save	try/Persist.aescene	save.Persist	panel.saves	gameplay	Saving games	6

Saving games

A save holds what you mark as persistent, not the whole scene. Loading a save reloads its scene from the project and then applies the save on top.

In Try it, the Checkpoint script saves after one second and then loads that save every few seconds. The green ball has Persist and comes back to where it was saved; the grey one has not and starts over from the scene file. In Try it saves stay in memory and are gone when the page closes.

Mark	What is saved
save.Persist component	the node's transform and enabled flag
sdk.Persist("field", …) on a component type	those fields of every such component
@persist on a script field	that field of every script instance
OnSave() / OnLoad()	values the script writes with save.Put*

Besides that a save remembers which scene nodes were destroyed and every object made with scene.Spawn: its prefab, parent, pose and persistent data.

@persist
var Coins int

func OnSave() {
  save.PutVec2("checkpoint", lastCheckpoint)
}

func OnLoad() {
  lastCheckpoint = save.GetVec2("checkpoint", node.Position())
}

Function
save.Save(slot)	write the game to a slot at the end of the frame
save.Load(slot)	reload the saved scene and restore the slot
save.Checkpoint()	save to the slot checkpoint
save.Autosave(seconds)	save to autosave every given number of real seconds
save.Exists(slot), save.Delete(slot)
save.SetGlobalInt(key, v), save.GlobalInt(key, def)	game-wide progress carried by every save; also Float, Bool, String

Slot names use letters, digits, - and _. Saves live next to the player settings, in saves/ of the profile.

---

id: save/load icon: file.open parent: save order: 1 title: Loading order

Loading order

Loading a save rebuilds the game in a fixed order. Knowing the order tells you which values a script already has in Ready and OnLoad.

1. The scene of the save is loaded fresh.
2. Scene nodes the save lists as destroyed are destroyed.
3. Spawned objects are spawned again with their persistent ids.
4. Transforms, component fields and @persist fields are restored.
5. Scripts run Ready, then OnLoad.

Fields restored in step 4 are already set when Ready runs. A field that is not marked comes from the scene, as on a fresh start.

References between saved nodes survive: a NodeRef to a scene node is saved by its id, a reference into a spawned object by the object's persistent id and the path inside it.

---

id: save/go icon: code.brackets parent: save order: 2 title: Modules

Modules

A module saves its own state with a section:

r.SaveSection("mygame.quests", questSection{})

A section has Version, Save(world, w), Load(world, r) and Migrate(node, from, to), which runs when a save was written by another version of the section. Sections of modules that are not loaded are kept and written back unchanged.