Godot GDScript: Advanced Patterns
Advanced patterns for scene management, save systems, performance optimization, and best practices.
Pattern 6: Scene Management
# scene_manager.gd (Autoload)
extends Node
signal scene_loading_started(scene_path: String)
signal scene_loading_progress(progress: float)
signal scene_loaded(scene: Node)
signal transition_started
signal transition_finished
@export var transition_scene: PackedScene
@export var loading_scene: PackedScene
var _current_scene: Node
var _transition: CanvasLayer
var _loader: ResourceLoader
func _ready() -> void:
_current_scene = get_tree().current_scene
if transition_scene:
_transition = transition_scene.instantiate()
add_child(_transition)
_transition.visible = false
func change_scene(scene_path: String, with_transition: bool = true) -> void:
if with_transition:
await _play_transition_out()
_load_scene(scene_path)
func change_scene_packed(scene: PackedScene, with_transition: bool = true) -> void:
if with_transition:
await _play_transition_out()
_swap_scene(scene.instantiate())
func _load_scene(path: String) -> void:
scene_loading_started.emit(path)
# Check if already loaded
if ResourceLoader.has_cached(path):
var scene := load(path) as PackedScene
_swap_scene(scene.instantiate())
return
# Async loading
ResourceLoader.load_threaded_request(path)
while true:
var progress := []
var status := ResourceLoader.load_threaded_get_status(path, progress)
match status:
ResourceLoader.THREAD_LOAD_IN_PROGRESS:
scene_loading_progress.emit(progress[0])
await get_tree().process_frame
ResourceLoader.THREAD_LOAD_LOADED:
var scene := ResourceLoader.load_threaded_get(path) as PackedScene
_swap_scene(scene.instantiate())
return
_:
push_error("Failed to load scene: %s" % path)
return
func _swap_scene(new_scene: Node) -> void:
if _current_scene:
_current_scene.queue_free()
_current_scene = new_scene
get_tree().root.add_child(_current_scene)
get_tree().current_scene = _current_scene
scene_loaded.emit(_current_scene)
await _play_transition_in()
func _play_transition_out() -> void:
if not _transition:
return
transition_started.emit()
_transition.visible = true
if _transition.has_method("transition_out"):
await _transition.transition_out()
else:
await get_tree().create_timer(0.3).timeout
func _play_transition_in() -> void:
if not _transition:
transition_finished.emit()
return
if _transition.has_method("transition_in"):
await _transition.transition_in()
else:
await get_tree().create_timer(0.3).timeout
_transition.visible = false
transition_finished.emit()Pattern 7: Save System
# save_manager.gd (Autoload)
extends Node
const SAVE_PATH := "user://savegame.save"
const ENCRYPTION_KEY := "your_secret_key_here"
signal save_completed
signal load_completed
signal save_error(message: String)
func save_game(data: Dictionary) -> void:
var file := FileAccess.open_encrypted_with_pass(
SAVE_PATH,
FileAccess.WRITE,
ENCRYPTION_KEY
)
if file == null:
save_error.emit("Could not open save file")
return
var json := JSON.stringify(data)
file.store_string(json)
file.close()
save_completed.emit()
func load_game() -> Dictionary:
if not FileAccess.file_exists(SAVE_PATH):
return {}
var file := FileAccess.open_encrypted_with_pass(
SAVE_PATH,
FileAccess.READ,
ENCRYPTION_KEY
)
if file == null:
save_error.emit("Could not open save file")
return {}
var json := file.get_as_text()
file.close()
var parsed := JSON.parse_string(json)
if parsed == null:
save_error.emit("Could not parse save data")
return {}
load_completed.emit()
return parsed
func delete_save() -> void:
if FileAccess.file_exists(SAVE_PATH):
DirAccess.remove_absolute(SAVE_PATH)
func has_save() -> bool:
return FileAccess.file_exists(SAVE_PATH)# saveable.gd (Attach to saveable nodes)
class_name Saveable
extends Node
@export var save_id: String
func _ready() -> void:
if save_id.is_empty():
save_id = str(get_path())
func get_save_data() -> Dictionary:
var parent := get_parent()
var data := {"id": save_id}
if parent is Node2D:
data["position"] = {"x": parent.position.x, "y": parent.position.y}
if parent.has_method("get_custom_save_data"):
data.merge(parent.get_custom_save_data())
return data
func load_save_data(data: Dictionary) -> void:
var parent := get_parent()
if data.has("position") and parent is Node2D:
parent.position = Vector2(data.position.x, data.position.y)
if parent.has_method("load_custom_save_data"):
parent.load_custom_save_data(data)Performance Tips
# 1. Cache node references
@onready var sprite := $Sprite2D # Good
# $Sprite2D in _process() # Bad - repeated lookup
# 2. Use object pooling for frequent spawning
# See Pattern 4 in the main skill
# 3. Avoid allocations in hot paths
var _reusable_array: Array = []
func _process(_delta: float) -> void:
_reusable_array.clear() # Reuse instead of creating new
# 4. Use static typing
func calculate(value: float) -> float: # Good
return value * 2.0
# 5. Disable processing when not needed
func _on_off_screen() -> void:
set_process(false)
set_physics_process(false)Best Practices
Do's
- Use signals for decoupling - Avoid direct references
- Type everything - Static typing catches errors
- Use resources for data - Separate data from logic
- Pool frequently spawned objects - Avoid GC hitches
- Use Autoloads sparingly - Only for truly global systems
Don'ts
- Don't use
get_node()in loops - Cache references - Don't couple scenes tightly - Use signals
- Don't put logic in resources - Keep them data-only
- Don't ignore the Profiler - Monitor performance
- Don't fight the scene tree - Work with Godot's design