Master Godot 4 GDScript patterns including signals, scenes, state machines, and optimization. Use when building Godot games, implementing game systems, or learning GDScript best practices.
Production patterns for Godot 4.x game development with GDScript, covering architecture, signals, scenes, and optimization.
Node: Base building block
├── Scene: Reusable node tree (saved as .tscn)
├── Resource: Data container (saved as .tres)
├── Signal: Event communication
└── Group: Node categorization
class_name Player
extends CharacterBody2D
# Signals
signal health_changed(new_health: int)
signal died
# Exports (Inspector-editable)
@export var speed: float = 200.0
@export var max_health: int = 100
@export_range(0, 1) var damage_reduction: float = 0.0
@export_group("Combat")
@export var attack_damage: int = 10
@export var attack_cooldown: float = 0.5
# Onready (initialized when ready)
@onready var sprite: Sprite2D = $Sprite2D
@onready var animation: AnimationPlayer = $AnimationPlayer
@onready var hitbox: Area2D = $Hitbox
# Private variables (convention: underscore prefix)
var _health: int
var _can_attack: bool = true
func _ready() -> void:
_health = max_health
func _physics_process(delta: float) -> void:
var direction := Input.get_vector("left", "right", "up", "down")
velocity = direction * speed
move_and_slide()
func take_damage(amount: int) -> void:
var actual_damage := int(amount * (1.0 - damage_reduction))
_health = max(_health - actual_damage, 0)
health_changed.emit(_health)
if _health <= 0:
died.emit()
# state_machine.gd
class_name StateMachine
extends Node
signal state_changed(from_state: StringName, to_state: StringName)
@export var initial_state: State
var current_state: State
var states: Dictionary = {}
func _ready() -> void:
# Register all State children
for child in get_children():
if child is State:
states[child.name] = child
child.state_machine = self
child.process_mode = Node.PROCESS_MODE_DISABLED
# Start initial state
if initial_state:
current_state = initial_state
current_state.process_mode = Node.PROCESS_MODE_INHERIT
current_state.enter()
func _process(delta: float) -> void:
if current_state:
current_state.update(delta)
func _physics_process(delta: float) -> void:
if current_state:
current_state.physics_update(delta)
func _unhandled_input(event: InputEvent) -> void:
if current_state:
current_state.handle_input(event)
func transition_to(state_name: StringName, msg: Dictionary = {}) -> void:
if not states.has(state_name):
push_error("State '%s' not found" % state_name)
return
var previous_state := current_state
previous_state.exit()
previous_state.process_mode = Node.PROCESS_MODE_DISABLED
current_state = states[state_name]
current_state.process_mode = Node.PROCESS_MODE_INHERIT
current_state.enter(msg)
state_changed.emit(previous_state.name, current_state.name)
# state.gd
class_name State
extends Node
var state_machine: StateMachine
func enter(_msg: Dictionary = {}) -> void:
pass
func exit() -> void:
pass
func update(_delta: float) -> void:
pass
func physics_update(_delta: float) -> void:
pass
func handle_input(_event: InputEvent) -> void:
pass
# player_idle.gd
class_name PlayerIdle
extends State
@export var player: Player
func enter(_msg: Dictionary = {}) -> void:
player.animation.play("idle")
func physics_update(_delta: float) -> void:
var direction := Input.get_vector("left", "right", "up", "down")
if direction != Vector2.ZERO:
state_machine.transition_to("Move")
func handle_input(event: InputEvent) -> void:
if event.is_action_pressed("attack"):
state_machine.transition_to("Attack")
elif event.is_action_pressed("jump"):
state_machine.transition_to("Jump")
# game_manager.gd (Add to Project Settings > Autoload)
extends Node
signal game_started
signal game_paused(is_paused: bool)
signal game_over(won: bool)
signal score_changed(new_score: int)
enum GameState { MENU, PLAYING, PAUSED, GAME_OVER }
var state: GameState = GameState.MENU
var score: int = 0:
set(value):
score = value
score_changed.emit(score)
var high_score: int = 0
func _ready() -> void:
process_mode = Node.PROCESS_MODE_ALWAYS
_load_high_score()
func _input(event: InputEvent) -> void:
if event.is_action_pressed("pause") and state == GameState.PLAYING:
toggle_pause()
func start_game() -> void:
score = 0
state = GameState.PLAYING
game_started.emit()
func toggle_pause() -> void:
var is_paused := state != GameState.PAUSED
if is_paused:
state = GameState.PAUSED
get_tree().paused = true
else:
state = GameState.PLAYING
get_tree().paused = false
game_paused.emit(is_paused)
func end_game(won: bool) -> void:
state = GameState.GAME_OVER
if score > high_score:
high_score = score
_save_high_score()
game_over.emit(won)
func add_score(points: int) -> void:
score += points
func _load_high_score() -> void:
if FileAccess.file_exists("user://high_score.save"):
var file := FileAccess.open("user://high_score.save", FileAccess.READ)
high_score = file.get_32()
func _save_high_score() -> void:
var file := FileAccess.open("user://high_score.save", FileAccess.WRITE)
file.store_32(high_score)
# event_bus.gd (Global signal bus)
extends Node
# Player events
signal player_spawned(player: Node2D)
signal player_died(player: Node2D)
signal player_health_changed(health: int, max_health: int)
# Enemy events
signal enemy_spawned(enemy: Node2D)
signal enemy_died(enemy: Node2D, position: Vector2)
# Item events
signal item_collected(item_type: StringName, value: int)
signal powerup_activated(powerup_type: StringName)
# Level events
signal level_started(level_number: int)
signal level_completed(level_number: int, time: float)
signal checkpoint_reached(checkpoint_id: int)
# weapon_data.gd
class_name WeaponData
extends Resource
@export var name: StringName
@export var damage: int
@export var attack_speed: float
@export var range: float
@export_multiline var description: String
@export var icon: Texture2D
@export var projectile_scene: PackedScene
@export var sound_attack: AudioStream
# character_stats.gd
class_name CharacterStats
extends Resource
signal stat_changed(stat_name: StringName, new_value: float)
@export var max_health: float = 100.0
@export var attack: float = 10.0
@export var defense: float = 5.0
@export var speed: float = 200.0
# Runtime values (not saved)
var _current_health: float
func _init() -> void:
_current_health = max_health
func get_current_health() -> float:
return _current_health
func take_damage(amount: float) -> float:
var actual_damage := maxf(amount - defense, 1.0)
_current_health = maxf(_current_health - actual_damage, 0.0)
stat_changed.emit("health", _current_health)
return actual_damage
func heal(amount: float) -> void:
_current_health = minf(_current_health + amount, max_health)
stat_changed.emit("health", _current_health)
func duplicate_for_runtime() -> CharacterStats:
var copy := duplicate() as CharacterStats
copy._current_health = copy.max_health
return copy
# Using resources
class_name Character
extends CharacterBody2D
@export var base_stats: CharacterStats
@export var weapon: WeaponData
var stats: CharacterStats
func _ready() -> void:
# Create runtime copy to avoid modifying the resource
stats = base_stats.duplicate_for_runtime()
stats.stat_changed.connect(_on_stat_changed)
func attack() -> void:
if weapon:
print("Attacking with %s for %d damage" % [weapon.name, weapon.damage])
func _on_stat_changed(stat_name: StringName, value: float) -> void:
if stat_name == "health" and value <= 0:
die()
# object_pool.gd
class_name ObjectPool
extends Node
@export var pooled_scene: PackedScene
@export var initial_size: int = 10
@export var can_grow: bool = true
var _available: Array[Node] = []
var _in_use: Array[Node] = []
func _ready() -> void:
_initialize_pool()
func _initialize_pool() -> void:
for i in initial_size:
_create_instance()
func _create_instance() -> Node:
var instance := pooled_scene.instantiate()
instance.process_mode = Node.PROCESS_MODE_DISABLED
instance.visible = false
add_child(instance)
_available.append(instance)
# Connect return signal if exists
if instance.has_signal("returned_to_pool"):
instance.returned_to_pool.connect(_return_to_pool.bind(instance))
return instance
func get_instance() -> Node:
var instance: Node
if _available.is_empty():
if can_grow:
instance = _create_instance()
_available.erase(instance)
else:
push_warning("Pool exhausted and cannot grow")
return null
else:
instance = _available.pop_back()
instance.process_mode = Node.PROCESS_MODE_INHERIT
instance.visible = true
_in_use.append(instance)
if instance.has_method("on_spawn"):
instance.on_spawn()
return instance
func _return_to_pool(instance: Node) -> void:
if not instance in _in_use:
return
_in_use.erase(instance)
if instance.has_method("on_despawn"):
instance.on_despawn()
instance.process_mode = Node.PROCESS_MODE_DISABLED
instance.visible = false
_available.append(instance)
func return_all() -> void:
for instance in _in_use.duplicate():
_return_to_pool(instance)
# pooled_bullet.gd
class_name PooledBullet
extends Area2D
signal returned_to_pool
@export var speed: float = 500.0
@export var lifetime: float = 5.0
var direction: Vector2
var _timer: float
func on_spawn() -> void:
_timer = lifetime
func on_despawn() -> void:
direction = Vector2.ZERO
func initialize(pos: Vector2, dir: Vector2) -> void:
global_position = pos
direction = dir.normalized()
rotation = direction.angle()
func _physics_process(delta: float) -> void:
position += direction * speed * delta
_timer -= delta
if _timer <= 0:
returned_to_pool.emit()
func _on_body_entered(body: Node2D) -> void:
if body.has_method("take_damage"):
body.take_damage(10)
returned_to_pool.emit()
# health_component.gd
class_name HealthComponent
extends Node
signal health_changed(current: int, maximum: int)
signal damaged(amount: int, source: Node)
signal healed(amount: int)
signal died
@export var max_health: int = 100
@export var invincibility_time: float = 0.0
var current_health: int:
set(value):
var old := current_health
current_health = clampi(value, 0, max_health)
if current_health != old:
health_changed.emit(current_health, max_health)
var _invincible: bool = false
func _ready() -> void:
current_health = max_health
func take_damage(amount: int, source: Node = null) -> int:
if _invincible or current_health <= 0:
return 0
var actual := mini(amount, current_health)
current_health -= actual
damaged.emit(actual, source)
if current_health <= 0:
died.emit()
elif invincibility_time > 0:
_start_invincibility()
return actual
func heal(amount: int) -> int:
var actual := mini(amount, max_health - current_health)
current_health += actual
if actual > 0:
healed.emit(actual)
return actual
func _start_invincibility() -> void:
_invincible = true
await get_tree().create_timer(invincibility_time).timeout
_invincible = false
# hitbox_component.gd
class_name HitboxComponent
extends Area2D
signal hit(hurtbox: HurtboxComponent)
@export var damage: int = 10
@export var knockback_force: float = 200.0
var owner_node: Node
func _ready() -> void:
owner_node = get_parent()
area_entered.connect(_on_area_entered)
func _on_area_entered(area: Area2D) -> void:
if area is HurtboxComponent:
var hurtbox := area as HurtboxComponent
if hurtbox.owner_node != owner_node:
hit.emit(hurtbox)
hurtbox.receive_hit(self)
# hurtbox_component.gd
class_name HurtboxComponent
extends Area2D
signal hurt(hitbox: HitboxComponent)
@export var health_component: HealthComponent
var owner_node: Node
func _ready() -> void:
owner_node = get_parent()
func receive_hit(hitbox: HitboxComponent) -> void:
hurt.emit(hitbox)
if health_component:
health_component.take_damage(hitbox.damage, hitbox.owner_node)
For advanced Godot patterns, performance tips, and best practices, see references/advanced-patterns.md:
SceneManager with async threaded loading (ResourceLoader.load_threaded_request), ResourceLoader.has_cached check, transition overlay support, and scene swapping with queue_freeSaveManager with AES-encrypted save files (FileAccess.open_encrypted_with_pass), JSON serialization, and a reusable Saveable component node for per-node save/load lifecycle@onready references, avoiding allocations in _process, static typing benefits, disabling processing for off-screen nodes
