先看看示例
作者提供的示例，实际效果取决于你的输入和使用工具。
输入
把这段使用Tween节点和setget的Godot 3脚本改写成Godot 4写法，并说明信号连接的变化。
输出
预期交付：逐项语法改写对照、迁移注意事项与常见报错处理建议。（编辑说明，非实际运行结果）
方法说明
---
name: godot-4-migration
description: "Specialized guide for migrating Godot 3.x projects to Godot 4 (GDScript 2.0), covering syntax changes, Tweens, and exports."
risk: safe
source: community
date_added: "2026-02-27"
---
# 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.
## Migration procedure
Work in a backed-up branch or copy. Choose an exact Godot 4 version, validate conversion before changing files, and inspect converter gaps, renamed nodes, shaders, physics, plugins and export targets. Test scenes and saved games before replacing the working Godot 3 build. Examples below are fragments in an appropriate Node script; `Enemy` must be a declared project type.
Official guide: [Upgrading to Godot 4](https://docs.godotengine.org/en/stable/tutorials/migrating/upgrading_to_godot_4.html).
## 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
signal health_changed(health: int)
var health: int = 100:
set(value):
health = value
emit_signal("health_changed", health)
get:
return health
```
### 3. Tween System
The Godot 3 `Tween` node was removed in Godot 4. 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 type checking; measure performance rather than assuming a speedup.
```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:** Use static types (`var x: int`) for clearer contracts and type checking; measure performance in the target engine and workload.
- ✅ **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:** Godot 4 uses a `Tween` object returned by `create_tween()`, not a scene node or a `SceneTreeTween` type. Use `var tween: Tween = create_tween()` in a Node context.
## Limitations
- Use this skill only when the task clearly matches the scope described above.
- Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
- Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.