Idiomatic way of removing specific entities

[nyvs]

Idiomatic way of removing specific entities

[nyvs]

Hi! Thank you so much. I now successfully moved from plain queries to all-systems, which works beautifully, and even better: everything works as expected. I must say I love legion.

[nyvs]

My current way of removing missiles looks like this:

fn remove_dead_missiles(world: &mut World) {
	let mut entity_list = vec![];
	let mut query = <Entity>::query();
	for entity in query.iter(world) {
		entity_list.push(*entity);
	}
	let mut to_delete = vec![];
	for e in entity_list {
		let ent = world.entry(e).unwrap();
		match ent.get_component::<Missile>() {
			Ok(m) => if m.is_set_off {
				to_delete.push(e);
			},
			Err(_) => (),
		}
	}
	for del in to_delete.iter() {
		world.remove(*del);
	}
}

[zedrian]

Hi @nyvs, not sure about the idiomatic way, but I can share with you my approach for solving such tasks.

All my logic is packed into systems generated via #[legion::system] macro (and executed in Schedule), so when I need to add/remove entities or components I simply request my system to access CommandBuffer and record corresponding commands into it.

In your case, such a system can look like this:

use legion::{Query, systems::CommandBuffer, world::SubWorld};

#[legion::system]
fn remove_exploded_missiles(objects: &mut Query<(Entity, &Missile)>,
                            commands: &mut CommandBuffer,
                            world: &mut SubWorld)
{
    for (entity, missile) in objects.iter(world) {
        if missile.is_set_off {
            commands.remove(entity);
        }
    }                    
}

Please let us know if this does not work for you.