Operation overload

DavidGasku

I have one problem I don't know how to resolve: I have a GeoLocation class, for which I want to implement some basic operations, like add. AFAIK, i can't overload basic operators like __+, so I tried to implement as regular functions:

    class_name GeoLocation
    
    var long: float setget set_long
    var lat: float setget set_lat
    
    func add(loc: GeoLocation) -> GeoLocation:
    	return GeoLocation.new(self.long + loc.long, self.lat + loc.lat)

But it throws Parser Error: Using own name in class file is not allowed (creates a cyclic reference) Is there any way I can return a new instance of the class? Thanks in advance

dotted

the class_name keyword is touchy and should not be thought of as being a class declaration in OO (C#,Java,C++ etc).

This is because a script that extends Spatial or Node etc can be assigned to any proper sub type of the extended node type, thus it is not a class

GDScript scripts are not class declarations but 'mixins' which are limited to the Object they may be applied to (like Node, or Spatial) by the extends statement

Consider class_name as a nickname for the script itself, which of the script must be fully loaded into the engine before the nickname can be referenced. This means that within the script itself, you can't really reference the nick name.

At least that is how I choose to think of it after starting to use class_name.

Instead of using GeoLocation use the parent Node's typename (likely a Spatial or Object)

func add(loc: Spatial) -> Spatial:

func add(loc: Object) -> Object:

Also note that memory management of Object is is manual. It isn't garbage collected. Nodes are the same way but will be automatically freed when children of another node that is deleted

I would highly recommend thinking of methods equivalent to += -= etc. as they don't imply new objects

Also I think you need to instance an object differently

see https://docs.godotengine.org/en/stable/classes/class_object.html#class-object

I suspect you should do:

var result:Object = Object.new()
result.set_script(get_script())
 // do  assign properties stuff after

or if you are using Spatial, duplicate self (self.duplicate() ) You don't need to set the script in this case.

note you can extend scripts by saying

extends "res://path-to-base-script.gd"

DavidGasku

I found that you can do the same thing by using get_script()

return get_script().new(self.long + loc.long, self.lat + loc.lat)

Is there any downside to this? Are they exactly the same?

dotted

I will also note that class_name can be subject to touchy cyclic reference errors in godot3.x. 4.0 may fix these but use class_name sparringly and not in a way where two class_named scripts reference each other.

It will be a cyclic error for godot

DavidGasku

so, isn't my solution safe? return get_script().new(self.long + loc.long, self.lat + loc.lat)

it seems that class_name that doesn't explicitly extends any Objects, automatically extends Reference, and it is therefore garbage collected (so you don't have to free it manually)

dotted

If godot accepts it, maybe it's ok.

Just keep in mind that there is a script object in the engine that represents the source code of gd-script which you have written and saved to a file which is then used to add functions and properties to a godot-engine object with object.set_script()

I am just a little worried you see that script is a godot-engine object that is-a Resource and think that is the godot-engine class that the gd-script text you write extends.

https://docs.godotengine.org/en/stable/classes/class_script.html