What is the Nil value? Is it the same as null?

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1

Godot Version

4.3

Question

What is the Nil?

Code from Learning-GDScript-by-Developing-a-Game-with-Godot-4/chapter07/player.gd at main · PacktPublishing/Learning-GDScript-by-Developing-a-Game-with-Godot-4 · GitHub

extends CharacterBody2D


const MAX_HEALTH: int = 10


@onready var _health_label: Label = $HealthLabel
func _ready():
	update_health_label()


func update_health_label():
	if not is_instance_valid(_health_label):
		return

	_health_label.text = str(health) + "/" + str(MAX_HEALTH)


func add_health_points(difference: int):
	health += difference

Why if remove if not is_instance_valid(_health_label): and change Health in Inspector for example 6 i se error

Invalid assignment of property or key ‘text’ with value of type ‘String’ on a base object of type ‘Nil’.

If is_instance_valid returns false then return is executed.
Return causes us to simply exit the function?

Then godot calls the code again and _health_label is already correct and returns true and this code from if is confused.

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2

Which line gives the error?

3

Nil represents that you’re variable was never initialized (I guess it’s the same as in Lua scripts).

For this case in particular, see if the Scene that you’re running contain $HealthLabel.

Also, if the $HealthLabel is a node from a scene being instantiated inside other scene, you should to pass the whole path to that node from the node that contains your script.
For example, if you have a Scene like:

CharacterBody2D
  Node
    HealthLabel

You will have to pass @onready var _health_label: Label = $‘Node/HealthLabel’
If otherwise, you have:

Node
  HealthLabel
CharacterBody2D

You will have to pass @onready var _health_label: Label = $‘…/Node/HealthLabel’

The two dots use is the same as in the cd command on Linux, it’s used to go one level upper in the hierarchy.

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