Registering constants

Constants can be used to share fixed values from Rust code to the Godot engine.

See also GDScript reference for constants.

Constant declaration

Constants are declared as const items in Rust, inside the inherent impl block of a class.

The attribute #[constant] makes it available to Godot.

fn main() {
impl Monster {
    const DEFAULT_HP: i32 = 100;

    fn from_name_hp(name: GString, hitpoints: i32) -> Gd<Self> { ... }

Usage in GDScript would look as follows:

var nom = Monster.from_name_hp("Nomster", Monster.DEFAULT_HP)
var orc = Monster.from_name_hp("Orc", 200)

(This particular example might be better suited for default parameters once they are implemented, but it illustrates the point.)


static fields can currently not be registered as constants.