Query Entity for single component

[HexSleeves]

Im building off "Hands on Rust", which is a book using bracket-lib and Legion, but im porting to use Bevy instead. There is a section to use tooltips where it queries all Entities by Name, Position and checks the entity for a health component.

positions
        .iter(ecs)
        .filter(|(_, pos, _)| **pos == map_pos )// (5)
        .for_each(|(entity, _, name) | {
            let screen_pos = *mouse_pos * 4;// (6)
            let display = if let Ok(health) = ecs.entry_ref(*entity)// (7)
                .unwrap()
                .get_component::<Health>() 
            {
                format!("{} : {} hp", &name.0, health.current)// (8)
            } else {// (9)
                name.0.clone()
            };
            draw_batch.print(screen_pos, &display);
        });

In my port, im doing the following:

pub fn tooltips(
    world: &World,
    input_state: Res<InputState>,
    camera_query: Query<&MainCamera>,
    positions: Query<(Entity, &Position, &Naming)>,
) {
    let camera = camera_query.single();
    let mouse_pos = input_state.mouse;
    let offset = Point::new(camera.left_x, camera.top_y);
    let map_pos = Position::from(mouse_pos + offset);

    let mut draw_batch = DrawBatch::new();
    draw_batch.target(2);

    for (ent, _, name) in positions.iter().filter(|(_, pos, _)| **pos == map_pos) {
        let screen_pos = mouse_pos * 4;

        let display = if let Some(health) = world.entity(ent).get::<Health>() {
            format!("{} ({}/{})", name.0, health.current, health.max)
        } else {
            name.0.clone()
        };

        draw_batch.print(screen_pos, &display);
    }
}

My question is there a way to check for a component on an entity without requiring the world? Seems odd that I have to pull the entire world to check if an entity has a component

[inquisitivecrystal]

I'm not in any way an experienced bevy user, so there's a substantial chance my advice will turn out to be wrong. That said, could you add Option<&Health> to your positions query, per this section of the documentation?

[ickk]

Yes, this is a good pattern to use in this case.

Alternatively, if all you have is an entity_id, you can create a second query:

query_health: Query<&Health>, 
...
query_health.get(entity)

[HexSleeves]

Thanks for the reply! This is perfect. Don't know how I missed this