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.

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

Gets the on_discard [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 relationship_accessor() -> Option<ComponentRelationshipAccessor<ChildOf>>

Returns [ComponentRelationshipAccessor] required for working with relationships in dynamic contexts.

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 FromTemplate for ChildOf

type Template = ChildOfTemplate

The Template for this type.

impl FromWorld for ChildOf

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

Creates Self using data from the given World.

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 Relationship for ChildOf

const ALLOW_SELF_REFERENTIAL: bool = false

If true, a relationship is allowed to point to its own entity.

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_discard(world: DeferredWorld<'_>, _: HookContext)

The on_discard component hook that maintains the [Relationship] / RelationshipTarget connection.

impl Eq for ChildOf

impl StructuralPartialEq for ChildOf

impl Unpin for ChildOf

where [()]: for<'a> SpecializeFromTemplate,