How to update a variable with a 'copy' of another variable inside a custom resource without updating the variable inside the resource

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1

Godot Version

4.4 Beta 3

Question

First of all, sorry if the title is confusing, I don’t know how to explain my problem better.

I have a variable outside my custom resource, to which I am assigning a variable inside my custom resource

class_name CustomResource
extends Resource

@export var a : Array[Array]

class_name Player 
extends CharacterBody2D

@export var custom_resource : CustomResource

extends Node2D

var a_player_resource : Array[Array]

@onready var player : Player = $Player

func _ready() -> void:
   a_player_resource = player.custom_resource.a

But when I want to update the variable outside of my custom resource by removing a parameter inside the ‘copy’ of the variable, I end up updating both variables.

func _input(event: InputEvent) -> void:
	if event.is_action_pressed('ui_up'):
		print('In Player', player.custom_resource.a)
		print('In Node2D', a_player_resource)
		a_player_resource[0].erase(1)
        print('In Player', player.custom_resource.a)
		print('In Node2D', a_player_resource)

The output of the print ends up being:

In Player[[1, 2], [2, 1]]
In Node2D[[1, 2], [2, 1]]
In Player[[2], [2, 1]]
In Node2D[[2], [2, 1]]

This does not happen if the variable is a number and I assume also any other type of variable that is not an array or dictionary.

This also happens in 4.3.

I don’t know if this is intentional or not, if it is please let me know.

Thank you very much in advance.

2

Only primitives are copied when passed, all other types are passed by reference. That means that both variables store a reference to the same entry on the heap.
If you want to copy a non primitive, you can use duplicate.

See GDScript reference — Godot Engine (stable) documentation in English

1 Like
3

Thank you!!