Questions about Autoloads

ProbablyTooAmbitious

1) So I used the arrows on the right of the Autoloads menu, and now I'm getting the "invalid get index on base nil" error in places where I used variables from the Autoload. So what difference does the order of the Autoloads make?

2) I tried to change a variable from an Autoload script in a different script, but it seems to act as both true and false? When I print it, it says both true and false one after the other. Is this to do with the variable originating from an Autoload, or is there another issue? This doesn't happen for any other variables in other scripts as far as I am aware.

Erich_L

If you're checking if something if true or false like this:

	if variable:
		print("is true")

This could also just mean that the variable is instantiated, or gettable. So in your example it's possible it returns false because it's not instantiated or ready then true when it can actually return the bool data type assigned to it.

In my most recent project I also use two auto loads but I had no urge whatsoever to have them crossover. I just put main global variables in one and some public information I needed to access after the game started in the other.

xyz

Autoloads are just nodes that are added to each scene before any of the regular scene nodes. They are siblings of your scene's top node. You can see this if you run a scene and then switch to "Remote" in the scene palette. First thing under the root viewport will be your autoloads, added in the order you specify in the preferences.

Knowing that, you can assume that all problems that can arise in inter-node communication for regular nodes, can also happen for autoloads.

The order matters. If you refer to something in an autoload from another autoload, it may happen that target autoload hasn't been added to the scene yet.

To get a more specific answer, try to make a minimal code/project that causes the problem and post it here.

cybereality

I'd assume the Autoloads on the top get created first, but I'd have to test it. In general though, Autoloads calling other Autoloads sounds sketchy. The Autoload is there to provide global access for the rest of the game. Calling each other sounds like a bad idea.

Megalomaniak

@xyz said: Autoloads are just nodes that are added to each scene before any of the regular scene nodes.

To the root scene(as siblings of your main node), it's probably worth noting that theres only one scene during runtime and everything else gets either appended to or removed from it.

xyz

@Megalomaniak said:

@xyz said: Autoloads are just nodes that are added to each scene before any of the regular scene nodes.

To the root scene(as siblings of your main node), it's probably worth noting that theres only one scene during runtime and everything else gets either appended to or removed from it.

Right. I should've phrased it better - autoloads are nodes added to the scene tree, as children of the root viewport, before any regular nodes are added.

TwistedTwigleg

@cybereality said: I'd assume the Autoloads on the top get created first, but I'd have to test it. ...

I've had several projects that rely on Autoloads and, at least with initialization, they are called first before child/main-scene nodes. :+1:

Also, something I only recently-ish learned with Autoload is that you can have a scene .tscn as an autoload. For a long time I thought it was only just .gd files that could be autoloads. If you use a scene, it will make an instance of it and it's children nodes, while if you use a .gd file, it will just make the top-level node of the same type as the script.

cybereality

That's good to know.

xyz

@TwistedTwigleg In my understanding, autoloads are just like regular nodes. You can do with them anything you can do with other nodes, so that includes scene instancing. However, because they are nodes, any .gd file you want to autoload must inherit at least from Node. Inheriting from Object or Reference would cause engine to complain and ignore the script.

TwistedTwigleg

@xyz said: @TwistedTwigleg In my understanding, autoloads are just like regular nodes. You can do with them anything you can do with other nodes, so that includes scene instancing. However, because they are nodes, any .gd file you want to autoload must inherit at least from Node. Inheriting from Object or Reference would cause engine to complain and ignore the script.

Yup! I just didn't realize you could select a .tscn file and it will instance everything in the .tscn file instead of just a single Node with the .gd script.

Erich_L

I understand everything @TwistedTwigleg said, but I still can't imagine why you'd autoload a scene? Isn't that the same idea as just... launching a chosen scene?

TwistedTwigleg

@Erich_L said: I understand everything @TwistedTwigleg said, but I still can't imagine why you'd autoload a scene? Isn't that the same idea as just... launching a chosen scene?

It is pretty similar, the only real difference I can see is that it wouldn't be destroyed automatically when changing scenes.

I could see it being useful if you wanted to split singleton/autoload functionality between multiple nodes, by having the child nodes handle functionality. Something like this, for example:

* Globals (autoload)
  * PlayerManager
  * EnemyManager
  * ItemManager

Then your autoload script could have something like this:

extends Node
var player_manager
var enemy_manager
var item_manager
func _ready():
	player_manager = get_node("PlayerManager")
	enemy_manager = get_node("EnemyManager")
	item_manager = get_node("ItemManager")

Then in scripts you could use it like Globals.player_manager or Globals.item_manager. Granted, you could just spawn the nodes and assign the scripts for each manager through the autoload script itself, but spawning a scene would remove the need for some of that code.

Megalomaniak

@Erich_L said: I understand everything @TwistedTwigleg said, but I still can't imagine why you'd autoload a scene? Isn't that the same idea as just... launching a chosen scene?

Think for an example of a scene that acts as your esc key menu overlay. It has a simple bool state that controls it's visibility and it defaults to false but your menu scene is always loaded and ready to be shown. Player just has to hit esc to show it.

Erich_L

Ahh actually very interesting, I will have fun mulling that over when structuring my next project. @Megalomaniak @TwistedTwigleg thanks a lot for the detailed explanation and suggestion.