can I get a Res from a World?

[atornity]

I'm making a thingy where I can add Modifiers to components and I want to be able to write stuff like

// where Health is a component and Score is a resource
let health_modifier = Modifier::new(|val: &mut Health, speed: &Speed, score: Res<Score>| {
    val.0 = speed.0 + score.0;
});
// this runs whenever Speed, Score or Base<Health> changes.

ok, the example doesn't make any sense but I want the first argument to be a specific component then every argument after that can be anything that implements ModParam which has a method for getting the stuff from the World.

So basically, I need a way of getting a Res from a World for this to work.

[alice-i-cecile]

You want one of the methods on World like World::resource.

If you run into troubles with the borrow checker, see resource_scope, SystemState or even one shot systems.

[atornity]

i can't use World::resource since it returns &T, not Res<T> but I'll check out SystemState tomorrow. Thanks!