Struct EntityRef 

pub struct EntityRef<'w> { /* private fields */ }

A read-only reference to a particular Entity and all of its components.

Examples

Read-only access disjoint with mutable access.

fn disjoint_system(
    query1: Query<&mut A>,
    query2: Query<EntityRef, Without<A>>,
) {
    // ...
}

Implementations

impl<'w> EntityRef<'w>

pub fn into_filtered(self) -> FilteredEntityRef<'w, 'static>

Consumes self and returns a FilteredEntityRef which has read-only access to all of the entity’s components, with the world 'w lifetime.

pub fn id(&self) -> Entity

Returns the ID of the current entity.

pub fn location(&self) -> EntityLocation

Gets metadata indicating the location where the current entity is stored.

pub fn archetype(&self) -> &Archetype

Returns the archetype that the current entity belongs to.

pub fn contains<T: Component>(&self) -> bool

Returns true if the current entity has a component of type T. Otherwise, this returns false.

Notes

If you do not know the concrete type of a component, consider using Self::contains_id or Self::contains_type_id.

pub fn contains_id(&self, component_id: ComponentId) -> bool

Returns true if the current entity has a component identified by component_id. Otherwise, this returns false.

Notes

• If you know the concrete type of the component, you should prefer Self::contains.
• If you know the component’s TypeId but not its ComponentId, consider using Self::contains_type_id.

pub fn contains_type_id(&self, type_id: TypeId) -> bool

Returns true if the current entity has a component with the type identified by type_id. Otherwise, this returns false.

Notes

• If you know the concrete type of the component, you should prefer Self::contains.
• If you have a ComponentId instead of a TypeId, consider using Self::contains_id.

pub fn get<T: Component>(&self) -> Option<&'w T>

Gets access to the component of type T for the current entity. Returns None if the entity does not have a component of type T.

pub fn get_ref<T: Component>(&self) -> Option<Ref<'w, T>>

Gets access to the component of type T for the current entity, including change detection information as a Ref.

Returns None if the entity does not have a component of type T.

pub fn get_change_ticks<T: Component>(&self) -> Option<ComponentTicks>

Retrieves the change ticks for the given component. This can be useful for implementing change detection in custom runtimes.

pub fn get_changed_by<T: Component>(&self) -> Option<MaybeLocation>

Get the MaybeLocation from where the given Component was last changed from. This contains information regarding the last place (in code) that changed this component and can be useful for debugging. For more information, see Location, and enable the track_location feature.

pub fn get_change_ticks_by_id( &self, component_id: ComponentId, ) -> Option<ComponentTicks>

Retrieves the change ticks for the given ComponentId. This can be useful for implementing change detection in custom runtimes.

You should prefer to use the typed API EntityRef::get_change_ticks where possible and only use this in cases where the actual component types are not known at compile time.

pub fn get_by_id<F: DynamicComponentFetch>( &self, component_ids: F, ) -> Result<F::Ref<'w>, EntityComponentError>

Returns untyped read-only reference(s) to component(s) for the current entity, based on the given ComponentIds.

You should prefer to use the typed API EntityRef::get where possible and only use this in cases where the actual component types are not known at compile time.

Unlike EntityRef::get, this returns untyped reference(s) to component(s), and it’s the job of the caller to ensure the correct type(s) are dereferenced (if necessary).

Errors

Returns EntityComponentError::MissingComponent if the entity does not have a component.

Examples

Single ComponentId

let entity = world.spawn(Foo(42)).id();

// Grab the component ID for `Foo` in whatever way you like.
let component_id = world.register_component::<Foo>();

// Then, get the component by ID.
let ptr = world.entity(entity).get_by_id(component_id);

Array of ComponentIds

let entity = world.spawn((X(42), Y(10))).id();

// Grab the component IDs for `X` and `Y` in whatever way you like.
let x_id = world.register_component::<X>();
let y_id = world.register_component::<Y>();

// Then, get the components by ID. You'll receive a same-sized array.
let Ok([x_ptr, y_ptr]) = world.entity(entity).get_by_id([x_id, y_id]) else {
    // Up to you to handle if a component is missing from the entity.
};

Slice of ComponentIds

let entity = world.spawn((X(42), Y(10))).id();

// Grab the component IDs for `X` and `Y` in whatever way you like.
let x_id = world.register_component::<X>();
let y_id = world.register_component::<Y>();

// Then, get the components by ID. You'll receive a vec of ptrs.
let ptrs = world.entity(entity).get_by_id(&[x_id, y_id] as &[ComponentId]);

HashSet of ComponentIds

let entity = world.spawn((X(42), Y(10))).id();

// Grab the component IDs for `X` and `Y` in whatever way you like.
let x_id = world.register_component::<X>();
let y_id = world.register_component::<Y>();

// Then, get the components by ID. You'll receive a vec of ptrs.
let ptrs = world.entity(entity).get_by_id(&HashSet::from_iter([x_id, y_id]));

pub fn components<Q: ReadOnlyQueryData + ReleaseStateQueryData + SingleEntityQueryData>( &self, ) -> Q::Item<'w, 'static>

Returns read-only components for the current entity that match the query Q.

Panics

If the entity does not have the components required by the query Q.

pub fn get_components<Q: ReadOnlyQueryData + ReleaseStateQueryData + SingleEntityQueryData>( &self, ) -> Result<Q::Item<'w, 'static>, QueryAccessError>

Returns read-only components for the current entity that match the query Q, or None if the entity does not have the components required by the query Q.

pub fn spawned_by(&self) -> MaybeLocation

Returns the source code location from which this entity has been spawned.

pub fn spawn_tick(&self) -> Tick

Returns the Tick at which this entity has been spawned.

Trait Implementations

impl<'w> Clone for EntityRef<'w>

fn clone(&self) -> EntityRef<'w>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl ContainsEntity for EntityRef<'_>

fn entity(&self) -> Entity

Returns the contained entity.

impl<'a> From<&'a EntityMut<'_>> for EntityRef<'a>

fn from(entity: &'a EntityMut<'_>) -> Self

Converts to this type from the input type.

impl<'a> From<&EntityRef<'a>> for FilteredEntityRef<'a, 'static>

fn from(entity: &EntityRef<'a>) -> Self

Converts to this type from the input type.

impl<'a> From<&'a EntityWorldMut<'_>> for EntityRef<'a>

fn from(entity: &'a EntityWorldMut<'_>) -> Self

Converts to this type from the input type.

impl<'w> From<EntityMut<'w>> for EntityRef<'w>

fn from(entity: EntityMut<'w>) -> Self

Converts to this type from the input type.

impl<'a> From<EntityRef<'a>> for FilteredEntityRef<'a, 'static>

fn from(entity: EntityRef<'a>) -> Self

Converts to this type from the input type.

impl<'w> From<EntityWorldMut<'w>> for EntityRef<'w>

fn from(entity: EntityWorldMut<'w>) -> EntityRef<'w>

Converts to this type from the input type.

impl Hash for EntityRef<'_>

fn hash<H: Hasher>(&self, state: &mut H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for EntityRef<'_>

fn cmp(&self, other: &Self) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl PartialEq for EntityRef<'_>

fn eq(&self, other: &Self) -> 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 PartialOrd for EntityRef<'_>

fn partial_cmp(&self, other: &Self) -> Option<Ordering>

EntityRef’s comparison trait implementations match the underlying Entity, and cannot discern between different worlds.

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

Tests less than (for self and other) and is used by the < operator.

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

Tests less than or equal to (for self and other) and is used by the <= operator.

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

Tests greater than (for self and other) and is used by the > operator.

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

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'a> QueryData for EntityRef<'a>

const IS_READ_ONLY: bool = true

True if this query is read-only and may not perform mutable access.

const IS_ARCHETYPAL: bool = true

Returns true if (and only if) this query data relies strictly on archetypes to limit which entities are accessed by the Query.

type ReadOnly = EntityRef<'a>

The read-only variant of this QueryData, which satisfies the ReadOnlyQueryData trait.

type Item<'w, 's> = EntityRef<'w>

The item returned by this WorldQuery This will be the data retrieved by the query, and is visible to the end user when calling e.g. Query<Self>::get.

fn shrink<'wlong: 'wshort, 'wshort, 's>( item: Self::Item<'wlong, 's>, ) -> Self::Item<'wshort, 's>

This function manually implements subtyping for the query items.

unsafe fn fetch<'w, 's>( _state: &'s Self::State, fetch: &mut Self::Fetch<'w>, entity: Entity, _table_row: TableRow, ) -> Option<Self::Item<'w, 's>>

Fetch Self::Item for either the given entity in the current Table, or for the given entity in the current Archetype. This must always be called after WorldQuery::set_table with a table_row in the range of the current Table or after WorldQuery::set_archetype with an entity in the current archetype. Accesses components registered in WorldQuery::update_component_access.

fn iter_access(_state: &Self::State) -> impl Iterator<Item = EcsAccessType<'_>>

Returns an iterator over the access needed by QueryData::fetch. Access conflicts are usually checked in WorldQuery::update_component_access, but in certain cases this method can be useful to implement a way of checking for access conflicts in a non-allocating way.

fn provide_extra_access( _state: &mut Self::State, _access: &mut Access, _available_access: &Access, )

Offers additional access above what we requested in update_component_access. Implementations may add additional access that is a subset of available_access and does not conflict with anything in access, and must update access to include that access.

impl ReleaseStateQueryData for EntityRef<'_>

fn release_state<'w>(item: Self::Item<'w, '_>) -> Self::Item<'w, 'static>

Releases the borrow from the query state by converting an item to have a 'static state lifetime.

impl<'a> TryFrom<&'a FilteredEntityMut<'_, '_>> for EntityRef<'a>

type Error = TryFromFilteredError

The type returned in the event of a conversion error.

fn try_from(entity: &'a FilteredEntityMut<'_, '_>) -> Result<Self, Self::Error>

Performs the conversion.

impl<'a> TryFrom<&FilteredEntityRef<'a, '_>> for EntityRef<'a>

type Error = TryFromFilteredError

The type returned in the event of a conversion error.

fn try_from(entity: &FilteredEntityRef<'a, '_>) -> Result<Self, Self::Error>

Performs the conversion.

impl<'a> TryFrom<FilteredEntityMut<'a, '_>> for EntityRef<'a>

type Error = TryFromFilteredError

The type returned in the event of a conversion error.

fn try_from(entity: FilteredEntityMut<'a, '_>) -> Result<Self, Self::Error>

Performs the conversion.

impl<'a> TryFrom<FilteredEntityRef<'a, '_>> for EntityRef<'a>

type Error = TryFromFilteredError

The type returned in the event of a conversion error.

fn try_from(entity: FilteredEntityRef<'a, '_>) -> Result<Self, Self::Error>

Performs the conversion.

impl<'a> WorldQuery for EntityRef<'a>

const IS_DENSE: bool = true

Returns true if (and only if) every table of every archetype matched by this fetch contains all of the matched components.

type Fetch<'w> = EntityFetch<'w>

Per archetype/table state retrieved by this WorldQuery to compute Self::Item for each entity.

type State = ()

State used to construct a Self::Fetch. This will be cached inside QueryState, so it is best to move as much data / computation here as possible to reduce the cost of constructing Self::Fetch.

fn shrink_fetch<'wlong: 'wshort, 'wshort>( fetch: Self::Fetch<'wlong>, ) -> Self::Fetch<'wshort>

This function manually implements subtyping for the query fetches.

unsafe fn init_fetch<'w, 's>( world: UnsafeWorldCell<'w>, _state: &'s Self::State, last_run: Tick, this_run: Tick, ) -> Self::Fetch<'w>

Creates a new instance of Self::Fetch, by combining data from the World with the cached Self::State. Readonly accesses resources registered in WorldQuery::update_component_access.

unsafe fn set_archetype<'w, 's>( _fetch: &mut Self::Fetch<'w>, _state: &'s Self::State, _archetype: &'w Archetype, _table: &Table, )

Adjusts internal state to account for the next Archetype. This will always be called on archetypes that match this WorldQuery.

unsafe fn set_table<'w, 's>( _fetch: &mut Self::Fetch<'w>, _state: &'s Self::State, _table: &'w Table, )

Adjusts internal state to account for the next Table. This will always be called on tables that match this WorldQuery.

fn update_component_access(_state: &Self::State, access: &mut FilteredAccess)

Adds any component accesses to the current entity used by this WorldQuery to access.

fn init_state(_world: &mut World)

Creates and initializes a State for this WorldQuery type.

fn get_state(_components: &Components) -> Option<()>

Attempts to initialize a State for this WorldQuery type using read-only access to Components.

fn matches_component_set( _state: &Self::State, _set_contains_id: &impl Fn(ComponentId) -> bool, ) -> bool

Returns true if this query matches a set of components. Otherwise, returns false.

fn init_nested_access( _state: &Self::State, _system_name: Option<&str>, _component_access_set: &mut FilteredAccessSet, _world: UnsafeWorldCell<'_>, )

Adds any component accesses to other entities used by this WorldQuery.

fn update_archetypes(_state: &mut Self::State, _world: UnsafeWorldCell<'_>)

Called when the query state is updating its archetype cache. This can be used by nested queries to update their internal archetype caches.

impl ArchetypeQueryData for EntityRef<'_>

impl<'w> Copy for EntityRef<'w>

impl EntityEquivalent for EntityRef<'_>

impl Eq for EntityRef<'_>

impl IterQueryData for EntityRef<'_>

impl ReadOnlyQueryData for EntityRef<'_>

impl SingleEntityQueryData for EntityRef<'_>