typecasting error ?

siska

I have a script that starts with : class_name HS extends Area

and another script that starts with : class_name HS_ia extends HS

The HS_ia script is empty.

Why am I not allowed to write this, inside the HS script : if self is HS_ia: print("+") // don't know how to indent properly here =/

=> editor ERROR : a value of type 'HS' will never be an instance of 'HS_ia'

cybereality

Maybe give HS_ia some variables or functions that make it different.

siska

Doesn't work either ... =/

cybereality

It should look like this:

extends Animal

class_name Cat

cybereality

But you can't test for the class inside the class. It needs to be external to the class structure. You can do this in a main script, or in an Autoload.

func _ready():
	var cat = Cat.new("Meow!")
	cat.say()
	print(cat is Cat) # this is True

siska

I'm not sure I understand what you're saying. ?

What I was trying to do, is have 1 script extend the other. The parent class is a 'general' hotspot (clickable), the child classes are more specialized hotspot types. When I click a hotspot, the code is directed to a method in the parent class.

I feel like I should be able to test, inside the parent class, what 'specialized' type the hotspot is ... ?

cybereality

In that case you should just override the hotspot function in the child class, then the correct one will always be called. Or you can use a generic function in the base class (if it's a lot of the same functionality) and then use variables that are specific to the child class to customize the behavior. You don't want to check the class name, as that is not inheritance, and not really any better than using a bunch of if-else statements.

siska

Thanks ! That will solve my problem, I think.

But just out of curiosity : why does what I did not work ? I mean, isn't that kind of like downcasting in other languages ?

cybereality

Because the base class doesn't know about child classes, and the child class can't check itself due to a cyclic reference error. I think you can do it in C++ because you can forward declare classes or use templates (or a dynamic_cast, even though it is sort of ugly) but I don't think GDScript is that advanced.

siska

Thank you for explaining !