setup-save-system

Setup Save System

Resource-backed save system. Survives reboots, handles typed data (Vector2, Color, Resources, custom classes), and uses a group + method convention so each persistable node owns its own serialization.

Why Resource over JSON

Format	Vector2 / Color	Resource refs	Custom classes	Human-readable
JSON	❌ string	❌	❌	✅
ConfigFile	✅	❌ (path only)	❌	✅
Resource (.tres)	✅	✅	✅	✅ (text)
Resource (.res)	✅	✅	✅	❌ (binary, faster)
FileAccess.store_var	✅	❌ (path only)	❌	❌

Use Resource for save data. JSON / ConfigFile are fine for settings (which are simple key-value).

Files to create

resources/save_data.gd

class_name SaveData
extends Resource
## Top-level save container. One file per slot.

@export var version: int = 1
@export var timestamp: int = 0
@export var play_time_seconds: float = 0.0
@export var current_scene: String = ""
@export var entries: Dictionary[NodePath, Variant] = {}

Bumping version lets you migrate old saves in SaveManager.load_game.

autoload/save_manager.gd

extends Node
## Resource-based save/load. Walks the "persist" group and calls
## save_data() / load_data() on each node. Per-node payloads are stored
## by NodePath in the SaveData.entries dictionary.

const SAVE_DIR := "user://saves/"
const VERSION := 1

signal save_started(slot: int)
signal save_finished(slot: int, ok: bool)
signal load_started(slot: int)
signal load_finished(slot: int, ok: bool)

# Cumulative play time across sessions. Previous form `Time.get_ticks_msec() / 1000.0`
# resets to engine-boot every save, throwing away prior sessions.
var _play_time_accum: float = 0.0
var _session_start_msec: int = 0

func _ready() -> void:
    _session_start_msec = Time.get_ticks_msec()

func save_game(slot: int) -> bool:
    save_started.emit(slot)
    DirAccess.make_dir_recursive_absolute(SAVE_DIR)
    var data := SaveData.new()
    data.version = VERSION
    data.timestamp = Time.get_unix_time_from_system()
    var now_msec: int = Time.get_ticks_msec()
    _play_time_accum += float(now_msec - _session_start_msec) / 1000.0
    _session_start_msec = now_msec
    data.play_time_seconds = _play_time_accum
    data.current_scene = get_tree().current_scene.scene_file_path if get_tree().current_scene else ""
    for node in get_tree().get_nodes_in_group("persist"):
        if node.has_method("save_data"):
            data.entries[node.get_path()] = node.save_data()
    var err := ResourceSaver.save(data, _path_for(slot))
    var ok := err == OK
    save_finished.emit(slot, ok)
    return ok

func load_game(slot: int) -> bool:
    load_started.emit(slot)
    var path := _path_for(slot)
    if not FileAccess.file_exists(path):
        load_finished.emit(slot, false)
        return false
    var data := load(path) as SaveData
    if data == null:
        load_finished.emit(slot, false)
        return false
    if data.version != VERSION:
        data = _migrate(data)
    _play_time_accum = data.play_time_seconds
    _session_start_msec = Time.get_ticks_msec()
    if data.current_scene != "" and data.current_scene != get_tree().current_scene.scene_file_path:
        await get_tree().create_timer(0.0).timeout  # let frame settle
        # Dynamic path from save → load() + change_scene_to_packed(); use preload() for static paths.
        var packed: PackedScene = load(data.current_scene) as PackedScene
        get_tree().change_scene_to_packed(packed)
        await get_tree().process_frame
    for node in get_tree().get_nodes_in_group("persist"):
        var entry: Variant = data.entries.get(node.get_path())
        if entry != null and node.has_method("load_data"):
            node.load_data(entry)
    load_finished.emit(slot, true)
    return true

func has_save(slot: int) -> bool:
    return FileAccess.file_exists(_path_for(slot))

func delete_save(slot: int) -> bool:
    var path := _path_for(slot)
    if not FileAccess.file_exists(path):
        return false
    return DirAccess.remove_absolute(path) == OK

func get_save_info(slot: int) -> SaveData:
    var path := _path_for(slot)
    if not FileAccess.file_exists(path):
        return null
    return load(path) as SaveData

func _path_for(slot: int) -> String:
    return "%sslot_%d.tres" % [SAVE_DIR, slot]

func _migrate(data: SaveData) -> SaveData:
    # add migrations here as VERSION bumps
    data.version = VERSION
    return data