Godot 4中connect()函数参数报错问题求助

参考Godot 3背包教程编写Godot 4代码时，inv_slot.connect("gui_input" , self , "slot_gui_input", [inv_slot])这行出现以下报错：

• 第9行：connect()调用参数过多，最多期望3个却收到4个
• 第9行：connect()函数参数2应为Callable类型，实际为res://Inventory/Item/Item.gd
• 第9行：无法将String类型的值作为int传递
• 第9行：connect()函数参数3应为int类型，实际为String

原代码 #

extends Node2D

const SlotClass = preload("res://Inventory/Slot.gd")
@onready var inventory_slots = $GridContainer
var holding_item = null

func _ready():
     for inv_slot in inventory_slots.get_children():
        inv_slot.connect("gui_input" , self , "slot_gui_input", [inv_slot])
        
func slot_gui_input(event: InputEvent, slot: SlotClass):
    if event is InputEventMouseButton:
        if event.button_index == MOUSE_BUTTON_LEFT & event.pressed:
            if holding_item != null:
                if !slot.item: # Place holding item to slot
                    slot.putIntoSlot(holding_item)
                    holding_item = null
            else: # Swap holding item with item in slot
                var temp_item = slot.item
                slot.PickFromSlot()
                temp_item.global_position = event.global_position
                slot.putIntoSlot(holding_item)
                holding_item = temp_item
        elif slot.item:
            holding_item = slot.item
            slot.pickFromSlot()
            holding_item.global_position = get_global_mouse_position()
func _input(event):
    if holding_item:
        holding_item.global_position = get_global_mouse_position()

问题根源与修复方案 #

Godot 4彻底修改了信号连接API，不再支持Godot 3中connect(signal, target, method, binds)的写法，改用Callable作为核心传递方式，参数绑定逻辑也同步调整。

1. 修复信号连接代码

将_ready()中的连接代码替换为以下两种写法之一：

• Callable绑定参数写法：

inv_slot.gui_input.connect(Callable(self, "slot_gui_input").bind(inv_slot))

• 匿名函数直观写法：

inv_slot.gui_input.connect(func(event): slot_gui_input(event, inv_slot))

2. 修复其他代码问题

原代码还有两处逻辑/格式错误：

• 逻辑判断event.button_index == MOUSE_BUTTON_LEFT & event.pressed中的&是位运算符，应改为逻辑与运算符&&
• slot.PickFromSlot()大小写不统一，与后续slot.pickFromSlot()保持一致，改为小写slot.pickFromSlot()

修改后的完整代码 #

extends Node2D

const SlotClass = preload("res://Inventory/Slot.gd")
@onready var inventory_slots = $GridContainer
var holding_item = null

func _ready():
     for inv_slot in inventory_slots.get_children():
        inv_slot.gui_input.connect(Callable(self, "slot_gui_input").bind(inv_slot))
        
func slot_gui_input(event: InputEvent, slot: SlotClass):
    if event is InputEventMouseButton:
        if event.button_index == MOUSE_BUTTON_LEFT && event.pressed:
            if holding_item != null:
                if !slot.item: # Place holding item to slot
                    slot.putIntoSlot(holding_item)
                    holding_item = null
            else: # Swap holding item with item in slot
                var temp_item = slot.item
                slot.pickFromSlot()
                temp_item.global_position = event.global_position
                slot.putIntoSlot(holding_item)
                holding_item = temp_item
        elif slot.item:
            holding_item = slot.item
            slot.pickFromSlot()
            holding_item.global_position = get_global_mouse_position()

func _input(event):
    if holding_item:
        holding_item.global_position = get_global_mouse_position()

内容的提问来源于stack exchange，提问作者Tieuacma