엔터티 생성하고 이동하기

Commands: 지연된 생성

fn setup(mut commands: Commands) {
    commands.spawn_empty();
}

Bundle로 생성하기

fn setup(mut commands: Commands) {
    commands.spawn((
        Position { x: 0.0, y: 0.0 },
        Velocity { x: 1.5, y: 0.0 },
        Player,
    ));
}

카메라로 보기

fn setup(mut commands: Commands) {
    commands.spawn(Camera2d::default());
}

스프라이트 생성하기

commands.spawn((
    Sprite::from_color(Color::srgb(0.2, 0.7, 1.0), Vec2::new(40.0, 40.0)),
    Transform::from_xyz(0.0, 0.0, 0.0),
    Velocity { x: 80.0, y: 0.0 },
));

Transform과 사용자 지정 Position 비교

#[derive(Component)]
struct Velocity { x: f32, y: f32 }

fn apply_velocity(mut q: Query<(&mut Transform, &Velocity)>) {
    for (mut tf, vel) in &mut q {
        tf.translation.x += vel.x;
        tf.translation.y += vel.y;
    }
}

가변적으로 쿼리 순회하기

fn move_all(mut q: Query<&mut Transform, With<Player>>) {
    for mut tf in &mut q {
        tf.translation.x += 1.0;
    }
}

여러 엔터티 생성하기

fn spawn_row(mut commands: Commands) {
    for i in 0..5 {
        commands.spawn((
            Sprite::from_color(Color::WHITE, Vec2::splat(20.0)),
            Transform::from_xyz(i as f32 * 30.0, 0.0, 0.0),
        ));
    }
}

엔터티 제거하기

fn cleanup(mut commands: Commands, q: Query<(Entity, &Transform)>) {
    for (e, tf) in &q {
        if tf.translation.y > 600.0 {
            commands.entity(e).despawn();
        }
    }
}

나중에 컴포넌트 추가하기

commands.entity(player).insert(Shield { hits: 3 });
// later
commands.entity(player).remove::<Shield>();

레이어링을 위한 Z

// background behind, player in front
commands.spawn((bg_sprite, Transform::from_xyz(0.0, 0.0, 0.0)));
commands.spawn((player_sprite, Transform::from_xyz(0.0, 0.0, 10.0)));

연결하여 실행하기

App::new()
    .add_plugins(DefaultPlugins)
    .add_systems(Startup, setup)
    .add_systems(Update, apply_velocity)
    .run();

빠른 확인

복습: 생성과 이동