Declaring variables in the right place....

BingBong

I have fixed the 'issue' but not sure why this happens,

I have a simple spawn scene but kept getting an error With the 'var's set in the function, this script works ok as expected... (a spawn every second in this case)

var scene = load("res://Src/Spiderlet.tscn")
var pop = load("res://Src/Others/Burst.tscn")

func _ready():
	pass

func _on_SpawnTimer_timeout():
	var player = scene.instance()
	var popped = pop.instance()
	popped.position = Vector2(1000, 475)
	get_parent().add_child(popped)
	
	player.position = Vector2(1000, 500)
	get_parent().add_child(player)

...but with the 'var's set at the start of the script, this one gives an error (on the second 'spawn', first one spawns ok) Invalid set index 'position' (on base: 'null instance') with value of type 'Vector2'.

var scene = load("res://Src/Spiderlet.tscn")
var pop = load("res://Src/Others/Burst.tscn")
var player = scene.instance()
var popped = pop.instance()

func _ready():
	pass

func _on_SpawnTimer_timeout():
	popped.position = Vector2(1000, 475)
	get_parent().add_child(popped)
	
	player.position = Vector2(1000, 500)
	get_parent().add_child(player)

Isnt the point of the variables declared at the top of the script mean they are globally accessable throughout the script?

Feels like this should work both ways.

Whats going on here?!

cybereality

You have to use onready for any variables that are more than simple types. So:

onready var scene = load("res://Src/Spiderlet.tscn")
onready var player = scene.instance()

This will ensure that the variables are initialized at the right time when the elements are ready.

BingBong

Yeah, I already tried using onready for variables at the top also, and it still gives the same error, and it points to line 10 where the problem is...

Now, if I remove lines 10 and 11, and only have the player spawn, with the variables at the top, things get strange....

The first spawned player, drops down to the floor as per normal physcs behaviour, but the second spawned player deletes the first spawned one and hangs in the air untl I hit one of the move keys, then drops down, but with the vars included in the _on_SpawnTimer_timeout function, I can have as many players spawned as I like without a glitch!

Once the pop instance has happened (its only a quick animated pop graphic and a sound to make the player spawn interesting) it queue_free()s as its never going to be needed again, dont know if tht makes a difference.

Cant get my head round this one! Some strange behaviour just with the positioning of the vars!

DaveTheCoder

What happens if you declare the variables at the top:

var player
var popped

and initialize them in the function?

func _on_SpawnTimer_timeout():
    player = scene.instance()
    popped = pop.instance()

I'm not clear on whether you want new instances of each of those every time SpawnTimer times out.

cybereality

If the spawn timer is repeating, you need the instance call in that function as that will create the new object. Otherwise you are modifying the old object (and adding it again to the scene) which is not what you want.

xyz

Nothing strange about it.

In your first example you make a new instance each time on_SpawnTimer_timeout() is entered. So that's all good.

In the second example however, instance is made only once when script initializes, and from then on you operate on the exact same instance each time script enters on_SpawnTimer_timeout(). Which means you're trying to add the same instance as a child multiple times over. Maybe you've even deleted it somewhere else in the script. That probably causes all the funky behavior.

Note that this is not a matter of variable scope. You can still declare your vars in script-wide scope, but if you make a new instance and assign it inside on_SpawnTimer_timeout() it'll work fine. Like this:

var scene = load("res://Src/Spiderlet.tscn")
var player

func _on_SpawnTimer_timeout():
	player = scene.instance()
	player.position = Vector2(1000, 500)
	get_parent().add_child(player)

BingBong

ahhHHHhh, that makes sense now! Yes one of those nodes does delete itself pretty much immediately, so that might not help confuse things!

I may have only blinded myself with where the var is, rather than what its actually doing here.

Thanks for the explaination!! This does help!