godot-4-migration

Original：🇺🇸 English
Translated

Specialized guide for migrating Godot 3.x projects to Godot 4 (GDScript 2.0), covering syntax changes, Tweens, and exports.

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godot-migrationgdscriptcode-migrationsyntax-updategame-development

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Godot 4 Migration Guide

Overview

A critical guide for developers transitioning from Godot 3.x to Godot 4. This skill focuses on the major syntax changes in GDScript 2.0, the new 
Tween
system, and 
export
annotation updates.

When to Use This Skill

  • Use when porting a Godot 3 project to Godot 4.
  • Use when encountering syntax errors after upgrading.
  • Use when replacing deprecated nodes (like 
    Tween
    node vs 
    create_tween
    ).
  • Use when updating 
    export
    variables to 
    @export
    annotations.

Key Changes

1. Annotations (
@
)

Godot 4 uses 
@
for keywords that modify behavior.
  • export var x
    -> 
    @export var x
  • onready var y
    -> 
    @onready var y
  • tool
    -> 
    @tool
    (at top of file)

2. Setters and Getters

Properties now define setters/getters inline.
Godot 3:
gdscript
var health setget set_health, get_health

func set_health(value):
    health = value
Godot 4:
gdscript
var health: int:
    set(value):
        health = value
        emit_signal("health_changed", health)
    get:
        return health

3. Tween System

The 
Tween
node is deprecated. Use 
create_tween()
in code.
Godot 3:
gdscript
$Tween.interpolate_property(...)
$Tween.start()
Godot 4:
gdscript
var tween = create_tween()
tween.tween_property($Sprite, "position", Vector2(100, 100), 1.0)
tween.parallel().tween_property($Sprite, "modulate:a", 0.0, 1.0)

4. Signal Connections

String-based connections are discouraged. Use callables.
Godot 3:
gdscript
connect("pressed", self, "_on_pressed")
Godot 4:
gdscript
pressed.connect(_on_pressed)

Examples

Example 1: Typed Arrays

GDScript 2.0 supports typed arrays for better performance and type safety.
gdscript
# Godot 3
var enemies = []

# Godot 4
var enemies: Array[Node] = []

func _ready():
    for child in get_children():
        if child is Enemy:
            enemies.append(child)

Example 2: Awaiting Signals (Coroutines)

yield
is replaced by 
await
.
Godot 3:
gdscript
yield(get_tree().create_timer(1.0), "timeout")
Godot 4:
gdscript
await get_tree().create_timer(1.0).timeout

Best Practices

  • ✅ Do: Use 
    @export_range
    , 
    @export_file
    , etc., for better inspector UI.
  • ✅ Do: Type all variables (
    var x: int
    ) for performance gains in GDScript 2.0.
  • ✅ Do: Use 
    super()
    to call parent methods instead of 
    .function_name()
    .
  • ❌ Don't: Use string names for signals (
    emit_signal("name")
    ) if you can use the signal object (
    name.emit()
    ).

Troubleshooting

Problem: "Identifier 'Tween' is not a valid type." Solution: 
Tween
is now 
SceneTreeTween
or just an object returned by 
create_tween()
. You rarely type it explicitly, just use 
var tween = create_tween()
.