Question: how to deal with optional fields of a component?

[Anton Zelenin]

I'm trying to use a couple of components:

#[derive(Component, Schematic, Reflect)]
#[reflect(Schematic)]
pub enum Direction {
    Up,
    Down,
    Left,
    Right,
}

#[derive(Component, Schematic, Reflect)]
#[reflect(Schematic)]
pub struct MovementDirection {
    pub x_axis: Option<Direction>,
    pub y_axis: Option<Direction>,
}

but I get an error from proto no registration found for type core::option::Option<expeditions::core::controls::components::Direction> when I try to spawn a player that has MovementDirection. How can I use a component with another component that is optional? It is working with standard types like String, but not with my components.

[Gino Valente]

Unfortunately with bevy_reflect, you need to manually monomorphize and register generic types. Bevy does this for a few types (i.e. Option<String>) but you have to do the same with your own types (until something like bevyengine/bevy#5781 is merged).

So in your case,you could do

app.register_type::<Option<Direction>>();

Note

If the derive macro doesn't automatically pick up your Option, you can add #[schematic(optional)] to your field.

[Anton Zelenin]

Unfortunately with bevy_reflect, you need to manually monomorphize and register generic types. Bevy does this for a few types (i.e. Option<String>) but you have to do the same with your own types (until something like bevyengine/bevy#5781 is merged).

So in your case,you could do

app.register_type::<Option<Direction>>();

Note If the derive macro doesn't automatically pick up your Option, you can add #[schematic(optional)] to your field.

Oh, great, it works! Thank you :)