Struct bevy::prelude::ChildBuilder

pub struct ChildBuilder<'a> { /* private fields */ }

Struct for building children entities and adding them to a parent entity.

Example

This example creates three entities, a parent and two children.

commands.spawn(MyBundle {}).with_children(|child_builder| {
    child_builder.spawn(MyChildBundle {});
    child_builder.spawn(MyChildBundle {});
});

Implementations

impl ChildBuilder<'_>

pub fn spawn(&mut self, bundle: impl Bundle) -> EntityCommands<'_>

Spawns an entity with the given bundle and inserts it into the parent entity’s Children. Also adds Parent component to the created entity.

Examples found in repository

examples/app/log_layers_ecs.rs (lines 145-148)

fn print_logs(
    mut events: EventReader<LogEvent>,
    mut commands: Commands,
    log_viewer_root: Query<Entity, With<LogViewerRoot>>,
) {
    let root_entity = log_viewer_root.single();

    commands.entity(root_entity).with_children(|child| {
        for event in events.read() {
            child.spawn(TextBundle::from_section(
                &event.message,
                TextStyle::default(),
            ));
        }
    });
}

examples/window/window_resizing.rs (lines 46-55)

fn setup_ui(mut cmd: Commands) {
    // Node that fills entire background
    cmd.spawn(NodeBundle {
        style: Style {
            width: Val::Percent(100.),
            ..default()
        },
        ..default()
    })
    .with_children(|root| {
        // Text where we display current resolution
        root.spawn((
            TextBundle::from_section(
                "Resolution",
                TextStyle {
                    font_size: 50.0,
                    ..default()
                },
            ),
            ResolutionText,
        ));
    });
}

examples/dev_tools/fps_overlay.rs (lines 47-56)

fn setup(mut commands: Commands) {
    // We need to spawn a camera (2d or 3d) to see the overlay
    commands.spawn(Camera2dBundle::default());

    // Instruction text
    commands
        .spawn(NodeBundle {
            style: Style {
                width: Val::Percent(100.0),
                height: Val::Percent(100.0),
                align_items: AlignItems::Center,
                justify_content: JustifyContent::Center,
                ..default()
            },
            ..default()
        })
        .with_children(|c| {
            c.spawn(TextBundle::from_section(
                concat!(
                    "Press 1 to change color of the overlay.\n",
                    "Press 2 to change size of the overlay."
                ),
                TextStyle {
                    font_size: 25.0,
                    ..default()
                },
            ));
        });
}

examples/games/loading_screen.rs (lines 95-98)

fn setup(mut commands: Commands) {
    let level_data = LevelData {
        unload_level_id: commands.register_one_shot_system(unload_current_level),
        level_1_id: commands.register_one_shot_system(load_level_1),
        level_2_id: commands.register_one_shot_system(load_level_2),
    };
    commands.insert_resource(level_data);

    // Spawns the UI that will show the user prompts.
    let text_style = TextStyle {
        font_size: 50.0,
        ..default()
    };
    commands
        .spawn(NodeBundle {
            background_color: BackgroundColor(Color::NONE),
            style: Style {
                justify_self: JustifySelf::Center,
                align_self: AlignSelf::FlexEnd,
                ..default()
            },
            ..default()
        })
        .with_children(|parent| {
            parent.spawn(TextBundle::from_section(
                "Press 1 or 2 to load a new scene.",
                text_style,
            ));
        });
}

// Selects the level you want to load.
fn level_selection(
    mut commands: Commands,
    keyboard: Res<ButtonInput<KeyCode>>,
    level_data: Res<LevelData>,
    loading_state: Res<LoadingState>,
) {
    // Only trigger a load if the current level is fully loaded.
    if let LoadingState::LevelReady = loading_state.as_ref() {
        if keyboard.just_pressed(KeyCode::Digit1) {
            commands.run_system(level_data.unload_level_id);
            commands.run_system(level_data.level_1_id);
        } else if keyboard.just_pressed(KeyCode::Digit2) {
            commands.run_system(level_data.unload_level_id);
            commands.run_system(level_data.level_2_id);
        }
    }
}

// Marker component for easier deletion of entities.
#[derive(Component)]
struct LevelComponents;

// Removes all currently loaded level assets from the game World.
fn unload_current_level(
    mut commands: Commands,
    mut loading_state: ResMut<LoadingState>,
    entities: Query<Entity, With<LevelComponents>>,
) {
    *loading_state = LoadingState::LevelLoading;
    for entity in entities.iter() {
        commands.entity(entity).despawn_recursive();
    }
}

fn load_level_1(
    mut commands: Commands,
    mut loading_data: ResMut<LoadingData>,
    asset_server: Res<AssetServer>,
) {
    // Spawn the camera.
    commands.spawn((
        Camera3dBundle {
            transform: Transform::from_xyz(155.0, 155.0, 155.0)
                .looking_at(Vec3::new(0.0, 40.0, 0.0), Vec3::Y),
            ..default()
        },
        LevelComponents,
    ));

    // Save the asset into the `loading_assets` vector.
    let fox = asset_server.load("models/animated/Fox.glb#Scene0");
    loading_data.loading_assets.push(fox.clone().into());
    // Spawn the fox.
    commands.spawn((
        SceneBundle {
            scene: fox.clone(),
            transform: Transform::from_xyz(0.0, 0.0, 0.0),
            ..default()
        },
        LevelComponents,
    ));

    // Spawn the light.
    commands.spawn((
        DirectionalLightBundle {
            transform: Transform::from_xyz(3.0, 3.0, 2.0).looking_at(Vec3::ZERO, Vec3::Y),
            directional_light: DirectionalLight {
                shadows_enabled: true,
                ..default()
            },
            ..default()
        },
        LevelComponents,
    ));
}

fn load_level_2(
    mut commands: Commands,
    mut loading_data: ResMut<LoadingData>,
    asset_server: Res<AssetServer>,
) {
    // Spawn the camera.
    commands.spawn((
        Camera3dBundle {
            transform: Transform::from_xyz(1.0, 1.0, 1.0)
                .looking_at(Vec3::new(0.0, 0.2, 0.0), Vec3::Y),
            ..default()
        },
        LevelComponents,
    ));

    // Spawn the helmet.
    let helmet_scene = asset_server.load("models/FlightHelmet/FlightHelmet.gltf#Scene0");
    loading_data
        .loading_assets
        .push(helmet_scene.clone().into());
    commands.spawn((
        SceneBundle {
            scene: helmet_scene.clone(),
            ..default()
        },
        LevelComponents,
    ));

    // Spawn the light.
    commands.spawn((
        DirectionalLightBundle {
            transform: Transform::from_xyz(3.0, 3.0, 2.0).looking_at(Vec3::ZERO, Vec3::Y),
            directional_light: DirectionalLight {
                shadows_enabled: true,
                ..default()
            },
            ..default()
        },
        LevelComponents,
    ));
}

// Monitors current loading status of assets.
fn update_loading_data(
    mut loading_data: ResMut<LoadingData>,
    mut loading_state: ResMut<LoadingState>,
    asset_server: Res<AssetServer>,
    pipelines_ready: Res<PipelinesReady>,
) {
    if !loading_data.loading_assets.is_empty() || !pipelines_ready.0 {
        // If we are still loading assets / pipelines are not fully compiled,
        // we reset the confirmation frame count.
        loading_data.confirmation_frames_count = 0;

        // Go through each asset and verify their load states.
        // Any assets that are loaded are then added to the pop list for later removal.
        let mut pop_list: Vec<usize> = Vec::new();
        for (index, asset) in loading_data.loading_assets.iter().enumerate() {
            if let Some(state) = asset_server.get_load_states(asset) {
                if let bevy::asset::RecursiveDependencyLoadState::Loaded = state.2 {
                    pop_list.push(index);
                }
            }
        }

        // Remove all loaded assets from the loading_assets list.
        for i in pop_list.iter() {
            loading_data.loading_assets.remove(*i);
        }

        // If there are no more assets being monitored, and pipelines
        // are compiled, then start counting confirmation frames.
        // Once enough confirmations have passed, everything will be
        // considered to be fully loaded.
    } else {
        loading_data.confirmation_frames_count += 1;
        if loading_data.confirmation_frames_count == loading_data.confirmation_frames_target {
            *loading_state = LoadingState::LevelReady;
        }
    }
}

// Marker tag for loading screen components.
#[derive(Component)]
struct LoadingScreen;

// Spawns the necessary components for the loading screen.
fn load_loading_screen(mut commands: Commands) {
    let text_style = TextStyle {
        font_size: 80.0,
        ..default()
    };

    // Spawn the UI and Loading screen camera.
    commands.spawn((
        Camera2dBundle {
            camera: Camera {
                order: 1,
                ..default()
            },
            ..default()
        },
        LoadingScreen,
    ));

    // Spawn the UI that will make up the loading screen.
    commands
        .spawn((
            NodeBundle {
                background_color: BackgroundColor(Color::BLACK),
                style: Style {
                    height: Val::Percent(100.0),
                    width: Val::Percent(100.0),
                    justify_content: JustifyContent::Center,
                    align_items: AlignItems::Center,
                    ..default()
                },
                ..default()
            },
            LoadingScreen,
        ))
        .with_children(|parent| {
            parent.spawn(TextBundle::from_sections([TextSection::new(
                "Loading...",
                text_style.clone(),
            )]));
        });
}

examples/ui/ui_material.rs (lines 40-51)

fn setup(mut commands: Commands, mut ui_materials: ResMut<Assets<CustomUiMaterial>>) {
    // Camera so we can see UI
    commands.spawn(Camera2dBundle::default());

    commands
        .spawn(NodeBundle {
            style: Style {
                width: Val::Percent(100.0),
                height: Val::Percent(100.0),
                align_items: AlignItems::Center,
                justify_content: JustifyContent::Center,
                ..default()
            },
            ..default()
        })
        .with_children(|parent| {
            parent.spawn(MaterialNodeBundle {
                style: Style {
                    position_type: PositionType::Absolute,
                    width: Val::Px(250.0),
                    height: Val::Px(250.0),
                    ..default()
                },
                material: ui_materials.add(CustomUiMaterial {
                    color: LinearRgba::WHITE.to_f32_array().into(),
                }),
                ..default()
            });
        });
}

examples/ui/font_atlas_debug.rs (lines 99-106)

fn setup(mut commands: Commands, asset_server: Res<AssetServer>, mut state: ResMut<State>) {
    let font_handle = asset_server.load("fonts/FiraSans-Bold.ttf");
    state.handle = font_handle.clone();
    commands.spawn(Camera2dBundle::default());
    commands
        .spawn(NodeBundle {
            background_color: Color::NONE.into(),
            style: Style {
                position_type: PositionType::Absolute,
                bottom: Val::ZERO,
                ..default()
            },
            ..default()
        })
        .with_children(|parent| {
            parent.spawn(TextBundle::from_section(
                "a",
                TextStyle {
                    font: font_handle,
                    font_size: 60.0,
                    color: YELLOW.into(),
                },
            ));
        });
    // We're seeding the PRNG here to make this example deterministic for testing purposes.
    // This isn't strictly required in practical use unless you need your app to be deterministic.
    commands.insert_resource(SeededRng(ChaCha8Rng::seed_from_u64(19878367467713)));
}

Additional examples can be found in:

• examples/games/game_menu.rs
• examples/3d/parenting.rs
• examples/3d/color_grading.rs
• examples/stress_tests/many_glyphs.rs
• examples/window/scale_factor_override.rs
• examples/ecs/state.rs
• examples/ecs/hierarchy.rs
• examples/math/render_primitives.rs
• examples/ecs/sub_states.rs
• examples/ui/button.rs
• examples/ui/relative_cursor_position.rs
• examples/games/alien_cake_addict.rs
• examples/window/multiple_windows.rs
• examples/3d/spherical_area_lights.rs
• examples/ui/ui_scaling.rs
• examples/ui/ui_texture_atlas.rs
• examples/stress_tests/many_buttons.rs
• examples/audio/spatial_audio_2d.rs
• examples/ui/overflow_debug.rs
• examples/ui/ui_texture_slice.rs
• examples/audio/spatial_audio_3d.rs
• examples/3d/motion_blur.rs
• examples/ui/transparency_ui.rs
• examples/ui/size_constraints.rs
• examples/ui/ui_texture_atlas_slice.rs
• examples/ui/viewport_debug.rs
• examples/time/virtual_time.rs
• examples/ui/render_ui_to_texture.rs
• examples/ecs/iter_combinations.rs
• examples/2d/sprite_slice.rs
• examples/stress_tests/bevymark.rs
• examples/ecs/computed_states.rs
• examples/tools/gamepad_viewer.rs
• examples/3d/spotlight.rs
• examples/ui/flex_layout.rs
• examples/stress_tests/many_foxes.rs
• examples/ui/overflow.rs
• examples/ui/display_and_visibility.rs
• examples/2d/text2d.rs
• examples/ui/z_index.rs
• examples/games/desk_toy.rs
• examples/3d/parallax_mapping.rs
• examples/3d/split_screen.rs
• examples/3d/shadow_biases.rs
• examples/ui/text_debug.rs
• examples/animation/animated_transform.rs
• examples/3d/blend_modes.rs
• examples/3d/lighting.rs
• examples/ui/grid.rs
• examples/ui/ui.rs

pub fn spawn_empty(&mut self) -> EntityCommands<'_>

Spawns an Entity with no components and inserts it into the parent entity’s Children. Also adds Parent component to the created entity.

pub fn parent_entity(&self) -> Entity

Returns the parent entity of this ChildBuilder.

pub fn add_command<C>(&mut self, command: C) -> &mut ChildBuilder<'_>

where C: Command,

Adds a command to be executed, like Commands::add.