Struct ChildOf 

pub struct ChildOf(pub Entity);

Stores the parent entity of this child entity with this component.

This is a Relationship component, and creates the canonical “parent / child” hierarchy. This is the “source of truth” component, and it pairs with the Children RelationshipTarget.

This relationship should be used for things like:

1. Organizing entities in a scene
2. Propagating configuration or data inherited from a parent, such as “visibility” or “world-space global transforms”.
3. Ensuring a hierarchy is despawned when an entity is despawned.

ChildOf contains a single “target” Entity. When ChildOf is inserted on a “source” entity, the “target” entity will automatically (and immediately, via a component hook) have a Children component inserted, and the “source” entity will be added to that Children instance.

If the ChildOf component is replaced with a different “target” entity, the old target’s Children will be automatically (and immediately, via a component hook) be updated to reflect that change.

Likewise, when the ChildOf component is removed, the “source” entity will be removed from the old target’s Children. If this results in Children being empty, Children will be automatically removed.

When a parent is despawned, all children (and their descendants) will also be despawned.

You can create parent-child relationships in a variety of ways. The most direct way is to insert a ChildOf component:

let root = world.spawn_empty().id();
let child1 = world.spawn(ChildOf(root)).id();
let child2 = world.spawn(ChildOf(root)).id();
let grandchild = world.spawn(ChildOf(child1)).id();

assert_eq!(&**world.entity(root).get::<Children>().unwrap(), &[child1, child2]);
assert_eq!(&**world.entity(child1).get::<Children>().unwrap(), &[grandchild]);

world.entity_mut(child2).remove::<ChildOf>();
assert_eq!(&**world.entity(root).get::<Children>().unwrap(), &[child1]);

world.entity_mut(root).despawn();
assert!(world.get_entity(root).is_err());
assert!(world.get_entity(child1).is_err());
assert!(world.get_entity(grandchild).is_err());

However if you are spawning many children, you might want to use the EntityWorldMut::with_children helper instead:

let mut child1 = Entity::PLACEHOLDER;
let mut child2 = Entity::PLACEHOLDER;
let mut grandchild = Entity::PLACEHOLDER;
let root = world.spawn_empty().with_children(|p| {
    child1 = p.spawn_empty().with_children(|p| {
        grandchild = p.spawn_empty().id();
    }).id();
    child2 = p.spawn_empty().id();
}).id();

assert_eq!(&**world.entity(root).get::<Children>().unwrap(), &[child1, child2]);
assert_eq!(&**world.entity(child1).get::<Children>().unwrap(), &[grandchild]);

Tuple Fields

0: Entity

Implementations

impl ChildOf

pub fn parent(&self) -> Entity

The parent entity of this child entity.

Examples found in repository

examples/ui/ghost_nodes.rs (line 112)

fn button_system(
    mut interaction_query: Query<(&Interaction, &ChildOf), (Changed<Interaction>, With<Button>)>,
    labels_query: Query<(&Children, &ChildOf), With<Button>>,
    mut text_query: Query<&mut Text>,
    mut counter_query: Query<&mut Counter>,
) {
    // Update parent counter on click
    for (interaction, child_of) in &mut interaction_query {
        if matches!(interaction, Interaction::Pressed) {
            let mut counter = counter_query.get_mut(child_of.parent()).unwrap();
            counter.0 += 1;
        }
    }

    // Update button labels to match their parent counter
    for (children, child_of) in &labels_query {
        let counter = counter_query.get(child_of.parent()).unwrap();
        let mut text = text_query.get_mut(children[0]).unwrap();

        **text = counter.0.to_string();
    }
}

examples/animation/gltf_skinned_mesh.rs (line 54)

fn joint_animation(
    time: Res<Time>,
    children: Query<&ChildOf, With<SkinnedMesh>>,
    parents: Query<&Children>,
    mut transform_query: Query<&mut Transform>,
) {
    // Iter skinned mesh entity
    for child_of in &children {
        // Mesh node is the parent of the skinned mesh entity.
        let mesh_node_entity = child_of.parent();
        // Get `Children` in the mesh node.
        let mesh_node_parent = parents.get(mesh_node_entity).unwrap();

        // First joint is the second child of the mesh node.
        let first_joint_entity = mesh_node_parent[1];
        // Get `Children` in the first joint.
        let first_joint_children = parents.get(first_joint_entity).unwrap();

        // Second joint is the first child of the first joint.
        let second_joint_entity = first_joint_children[0];
        // Get `Transform` in the second joint.
        let mut second_joint_transform = transform_query.get_mut(second_joint_entity).unwrap();

        second_joint_transform.rotation =
            Quat::from_rotation_z(FRAC_PI_2 * ops::sin(time.elapsed_secs()));
    }
}

examples/3d/visibility_range.rs (line 190)

fn set_visibility_ranges(
    mut commands: Commands,
    mut new_meshes: Query<Entity, Added<Mesh3d>>,
    children: Query<(Option<&ChildOf>, Option<&MainModel>)>,
) {
    // Loop over each newly-added mesh.
    for new_mesh in new_meshes.iter_mut() {
        // Search for the nearest ancestor `MainModel` component.
        let (mut current, mut main_model) = (new_mesh, None);
        while let Ok((child_of, maybe_main_model)) = children.get(current) {
            if let Some(model) = maybe_main_model {
                main_model = Some(model);
                break;
            }
            match child_of {
                Some(child_of) => current = child_of.parent(),
                None => break,
            }
        }

        // Add the `VisibilityRange` component.
        match main_model {
            Some(MainModel::HighPoly) => {
                commands
                    .entity(new_mesh)
                    .insert(NORMAL_VISIBILITY_RANGE_HIGH_POLY.clone())
                    .insert(MainModel::HighPoly);
            }
            Some(MainModel::LowPoly) => {
                commands
                    .entity(new_mesh)
                    .insert(NORMAL_VISIBILITY_RANGE_LOW_POLY.clone())
                    .insert(MainModel::LowPoly);
            }
            None => {}
        }
    }
}

examples/3d/mixed_lighting.rs (line 462)

fn move_sphere(
    mouse_button_input: Res<ButtonInput<MouseButton>>,
    pointers: Query<&PointerInteraction>,
    mut meshes: Query<(&GltfMeshName, &ChildOf), With<Mesh3d>>,
    mut transforms: Query<&mut Transform>,
    app_status: Res<AppStatus>,
) {
    // Only run when the left button is clicked and we're not in baked lighting
    // mode.
    if app_status.lighting_mode == LightingMode::Baked
        || !mouse_button_input.pressed(MouseButton::Left)
    {
        return;
    }

    // Find the sphere.
    let Some(child_of) = meshes
        .iter_mut()
        .filter_map(|(name, child_of)| {
            if &**name == "Sphere" {
                Some(child_of)
            } else {
                None
            }
        })
        .next()
    else {
        return;
    };

    // Grab its transform.
    let Ok(mut transform) = transforms.get_mut(child_of.parent()) else {
        return;
    };

    // Set its transform to the appropriate position, as determined by the
    // picking subsystem.
    for interaction in pointers.iter() {
        if let Some(&(
            _,
            HitData {
                position: Some(position),
                ..
            },
        )) = interaction.get_nearest_hit()
        {
            transform.translation = position + vec3(0.0, SPHERE_OFFSET, 0.0);
        }
    }
}

Trait Implementations

impl Clone for ChildOf

fn clone(&self) -> ChildOf

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Component for ChildOf

where ChildOf: Send + Sync + 'static,

const STORAGE_TYPE: StorageType = bevy_ecs::component::StorageType::Table

A constant indicating the storage type used for this component.

type Mutability = Immutable

A marker type to assist Bevy with determining if this component is mutable, or immutable. Mutable components will have Component<Mutability = Mutable>, while immutable components will instead have Component<Mutability = Immutable>.

fn register_required_components( _requiree: ComponentId, required_components: &mut RequiredComponentsRegistrator<'_, '_>, )

Registers required components.

fn on_insert() -> Option<for<'w> fn(DeferredWorld<'w>, HookContext)>

Gets the on_insert ComponentHook for this Component if one is defined.

fn on_replace() -> Option<for<'w> fn(DeferredWorld<'w>, HookContext)>

Gets the on_replace ComponentHook for this Component if one is defined.

fn clone_behavior() -> ComponentCloneBehavior

Called when registering this component, allowing to override clone function (or disable cloning altogether) for this component.

fn map_entities<M>(this: &mut ChildOf, mapper: &mut M)

where M: EntityMapper,

Maps the entities on this component using the given EntityMapper. This is used to remap entities in contexts like scenes and entity cloning. When deriving Component, this is populated by annotating fields containing entities with #[entities]

fn on_add() -> Option<for<'w> fn(DeferredWorld<'w>, HookContext)>

Gets the on_add ComponentHook for this Component if one is defined.

fn on_remove() -> Option<for<'w> fn(DeferredWorld<'w>, HookContext)>

Gets the on_remove ComponentHook for this Component if one is defined.

fn on_despawn() -> Option<for<'w> fn(DeferredWorld<'w>, HookContext)>

Gets the on_despawn ComponentHook for this Component if one is defined.

impl Debug for ChildOf

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for ChildOf

fn deserialize<__D>( __deserializer: __D, ) -> Result<ChildOf, <__D as Deserializer<'de>>::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl FromArg for ChildOf

type This<'from_arg> = ChildOf

The type to convert into.

fn from_arg(arg: Arg<'_>) -> Result<<ChildOf as FromArg>::This<'_>, ArgError>

Creates an item from an argument.

impl FromReflect for ChildOf

fn from_reflect(reflect: &(dyn PartialReflect + 'static)) -> Option<ChildOf>

Constructs a concrete instance of Self from a reflected value.

fn take_from_reflect( reflect: Box<dyn PartialReflect>, ) -> Result<Self, Box<dyn PartialReflect>>

Attempts to downcast the given value to Self using, constructing the value using from_reflect if that fails.

impl FromWorld for ChildOf

fn from_world(_world: &mut World) -> ChildOf

Creates Self using data from the given World.

impl GetOwnership for ChildOf

fn ownership() -> Ownership

Returns the ownership of Self.

impl GetTypeRegistration for ChildOf

fn get_type_registration() -> TypeRegistration

Returns the default TypeRegistration for this type.

fn register_type_dependencies(registry: &mut TypeRegistry)

Registers other types needed by this type.

impl IntoReturn for ChildOf

fn into_return<'into_return>(self) -> Return<'into_return>

where ChildOf: 'into_return,

Converts Self into a Return value.

impl PartialEq for ChildOf

fn eq(&self, other: &ChildOf) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialReflect for ChildOf

fn get_represented_type_info(&self) -> Option<&'static TypeInfo>

Returns the TypeInfo of the type represented by this value.

fn try_apply( &mut self, value: &(dyn PartialReflect + 'static), ) -> Result<(), ApplyError>

Tries to apply a reflected value to this value.

fn reflect_kind(&self) -> ReflectKind

Returns a zero-sized enumeration of “kinds” of type.

fn reflect_ref(&self) -> ReflectRef<'_>

Returns an immutable enumeration of “kinds” of type.

fn reflect_mut(&mut self) -> ReflectMut<'_>

Returns a mutable enumeration of “kinds” of type.

fn reflect_owned(self: Box<ChildOf>) -> ReflectOwned

Returns an owned enumeration of “kinds” of type.

fn try_into_reflect( self: Box<ChildOf>, ) -> Result<Box<dyn Reflect>, Box<dyn PartialReflect>>

Attempts to cast this type to a boxed, fully-reflected value.

fn try_as_reflect(&self) -> Option<&(dyn Reflect + 'static)>

Attempts to cast this type to a fully-reflected value.

fn try_as_reflect_mut(&mut self) -> Option<&mut (dyn Reflect + 'static)>

Attempts to cast this type to a mutable, fully-reflected value.

fn into_partial_reflect(self: Box<ChildOf>) -> Box<dyn PartialReflect>

Casts this type to a boxed, reflected value.

fn as_partial_reflect(&self) -> &(dyn PartialReflect + 'static)

Casts this type to a reflected value.

fn as_partial_reflect_mut(&mut self) -> &mut (dyn PartialReflect + 'static)

Casts this type to a mutable, reflected value.

fn reflect_partial_eq( &self, value: &(dyn PartialReflect + 'static), ) -> Option<bool>

Returns a “partial equality” comparison result.

fn debug(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Debug formatter for the value.

fn reflect_clone(&self) -> Result<Box<dyn Reflect>, ReflectCloneError>

Attempts to clone Self using reflection.

fn apply(&mut self, value: &(dyn PartialReflect + 'static))

Applies a reflected value to this value.

fn to_dynamic(&self) -> Box<dyn PartialReflect>

Converts this reflected value into its dynamic representation based on its kind.

fn reflect_clone_and_take<T>(&self) -> Result<T, ReflectCloneError>

where T: 'static, Self: Sized + TypePath,

For a type implementing PartialReflect, combines reflect_clone and take in a useful fashion, automatically constructing an appropriate ReflectCloneError if the downcast fails.

fn reflect_hash(&self) -> Option<u64>

Returns a hash of the value (which includes the type).

fn is_dynamic(&self) -> bool

Indicates whether or not this type is a dynamic type.

impl Reflect for ChildOf

fn into_any(self: Box<ChildOf>) -> Box<dyn Any>

Returns the value as a Box<dyn Any>.

fn as_any(&self) -> &(dyn Any + 'static)

Returns the value as a &dyn Any.

fn as_any_mut(&mut self) -> &mut (dyn Any + 'static)

Returns the value as a &mut dyn Any.

fn into_reflect(self: Box<ChildOf>) -> Box<dyn Reflect>

Casts this type to a boxed, fully-reflected value.

fn as_reflect(&self) -> &(dyn Reflect + 'static)

Casts this type to a fully-reflected value.

fn as_reflect_mut(&mut self) -> &mut (dyn Reflect + 'static)

Casts this type to a mutable, fully-reflected value.

fn set(&mut self, value: Box<dyn Reflect>) -> Result<(), Box<dyn Reflect>>

Performs a type-checked assignment of a reflected value to this value.

impl Relationship for ChildOf

type RelationshipTarget = Children

The Component added to the “target” entities of this Relationship, which contains the list of all “source” entities that relate to the “target”.

fn get(&self) -> Entity

Gets the Entity ID of the related entity.

fn from(entity: Entity) -> ChildOf

Creates this Relationship from the given entity.

fn set_risky(&mut self, entity: Entity)

Changes the current Entity ID of the entity containing the RelationshipTarget to another one.

fn on_insert(world: DeferredWorld<'_>, _: HookContext)

The on_insert component hook that maintains the Relationship / RelationshipTarget connection.

fn on_replace(world: DeferredWorld<'_>, _: HookContext)

The on_replace component hook that maintains the Relationship / RelationshipTarget connection.

impl Serialize for ChildOf

fn serialize<__S>( &self, __serializer: __S, ) -> Result<<__S as Serializer>::Ok, <__S as Serializer>::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl TupleStruct for ChildOf

fn field(&self, index: usize) -> Option<&(dyn PartialReflect + 'static)>

Returns a reference to the value of the field with index index as a &dyn Reflect.

fn field_mut( &mut self, index: usize, ) -> Option<&mut (dyn PartialReflect + 'static)>

Returns a mutable reference to the value of the field with index index as a &mut dyn Reflect.

fn field_len(&self) -> usize

Returns the number of fields in the tuple struct.

fn iter_fields(&self) -> TupleStructFieldIter<'_>

Returns an iterator over the values of the tuple struct’s fields.

fn to_dynamic_tuple_struct(&self) -> DynamicTupleStruct

Creates a new DynamicTupleStruct from this tuple struct.

fn get_represented_tuple_struct_info(&self) -> Option<&'static TupleStructInfo>

Will return None if TypeInfo is not available.

impl TypePath for ChildOf

fn type_path() -> &'static str

Returns the fully qualified path of the underlying type.

fn short_type_path() -> &'static str

Returns a short, pretty-print enabled path to the type.

fn type_ident() -> Option<&'static str>

Returns the name of the type, or None if it is anonymous.

fn crate_name() -> Option<&'static str>

Returns the name of the crate the type is in, or None if it is anonymous.

fn module_path() -> Option<&'static str>

Returns the path to the module the type is in, or None if it is anonymous.

impl Typed for ChildOf

fn type_info() -> &'static TypeInfo

Returns the compile-time info for the underlying type.

impl Eq for ChildOf

impl StructuralPartialEq for ChildOf