Bevy ECS Markers

Adds the support for marking entites and fetching them in queries

Example

View more examples here

#[derive(EntityMarker)]
enum Players {
    Red,
    Blue,
    Green,
    Yellow,
}

#[derive(Component)]
struct Player {
    field: usize,
}

fn main() {
    App::new()
        .add_plugins(LogPlugin::default())
        .init_marker::<Players>()
        .add_systems(Startup, (setup, move_red_player).chain())
        .run();
}

fn setup(mut commands: Commands, mut players: MarkerMut<Players>) {
    players[Players::Red].assign(commands.spawn(Player { field: 2 }).id());
    players[Players::Blue].assign(commands.spawn(Player { field: 5 }).id());
    players[Players::Green].assign(commands.spawn(Player { field: 7 }).id());
    players[Players::Yellow].assign(commands.spawn(Player { field: 1 }).id());
}

fn move_red_player(mut query: Query<&mut Player>, current: Marker<Players>) {
    let Ok(mut player) = query.get_mut(current[Players::Red].id()) else {
        warn!("Red Player not set yet!");
        return;
    };

    let old = player.field;
    player.field += 2;
    let new = player.field;

    info!("Player moved from field {old} to field {new}");
}

License

• MIT License (LICENSE-MIT or http://opensource.org/licenses/MIT)
• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)

at your option.