Is there a way to instance a class based on a string or enum in GDScript?

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:information_source: Attention Topic was automatically imported from the old Question2Answer platform.
:bust_in_silhouette: Asked By Ramshell

I’d like to do something like

config.gd

extend Resource
class_name Config
enum Configuration { Option1, Option2, Option3 }
export(Configuration) var how_to_do_something = Option1

builder.gd

build(config : Config) -> OptionStrategy:
  # id like to do something like this to instance
  # the strategy classes Option1, Option2, Opntion3, and so on
  # get_class(config.how_to_do_something.string).new()

It might sound senseless. But I know that I will add more Options in the future, and I don’t want to maintain a match case in the builder for each Option I implement.

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:bust_in_silhouette: Reply From: Zylann

I’m not aware of a way to instance by name from a string, but I know it’s possible to do it if you have the path of the script resource (i.e res://scripts/my_script.gd):

var instance = load(path_to_script).new()

Which btw is how scripts are deserialized in the first place :stuck_out_tongue: That’s what I did to implement savegames in my last game jam (along with a few selected properties).

I’ve been searching in the web about this. And sadly, it seems that it is not possible to convert enums to strings automatically. But yeah, I guess that doing load("%s.gd" % option_string_representation) would do the trick if I happen to have the string.

Ramshell | 2019-10-23 13:21

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:bust_in_silhouette: Reply From: MintSoda

For engine classes, use ClassDB.instance("ClassName")

For custom classes, it’s only possible to instance from script path. Also, script paths can be found at ProjectSettings.get_setting("_global_script_classes"). So it’s possible to get the script of a class by its class_name, even if you move the scripts around.

Or use a class from godot-next, ClassType, which implements everything about class for you. (Somehow it was slow last year I used it, I only use it for creating plugins though. )

To be honest, I don’t know why custom classes aren’t included in ClassDB. This is very inconvenient.

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:bust_in_silhouette: Reply From: exuin

For Godot 4, you can use the ClassDB method for built-in classes like MintSoda said. For custom classes, call ProjectSettings — Godot Engine (stable) documentation in English and iterate through the array to find the class you’re looking for. Then load it.

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As of Godot 4.2 the method name has changed,

use ClassDB.instantiate("ClassName") as per the documentation

This is particularly helpful when using @tool mode where you need to use the class EditorPlugin.new() but if you run this in-game it’ll give the error

Parser Error: Native class “EditorPlugin” cannot be constructed as it is abstract.

image

Just replace it with

func _ready():
	if(Engine.is_editor_hint()):
		var _editor_plugin=ClassDB.instantiate("EditorPlugin")
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