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 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_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(&self, component_id: ComponentId) -> Option<Ptr<'w>>

Gets the component of the given ComponentId from the entity.

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

Unlike EntityRef::get, this returns a raw pointer to the component, which is only valid while the 'w borrow of the lifetime is active.

Trait Implementations

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

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

Returns a copy of the value.

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

Performs copy-assignment from source.

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

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

Converts to this type from the input type.

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

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

Converts to this type from the input type.

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

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

Converts to this type from the input type.

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

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

Converts to this type from the input type.

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

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_mut: EntityWorldMut<'w>) -> EntityRef<'w>

Converts to this type from the input type.

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

SAFETY: Self is the same as Self::ReadOnly

type ReadOnly = EntityRef<'a>

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

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

type Error = TryFromFilteredError

The type returned in the event of a conversion error.

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

Performs the conversion.

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

type Error = TryFromFilteredError

The type returned in the event of a conversion error.

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

Performs the conversion.

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

SAFETY: fetch accesses all components in a readonly way. This is sound because update_component_access and update_archetype_component_access set read access for all components and panic when appropriate. Filters are unchanged.

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. This is used to select a more efficient “table iterator” for “dense” queries. If this returns true, WorldQuery::set_table must be used before WorldQuery::fetch can be called for iterators. If this returns false, WorldQuery::set_archetype must be used before WorldQuery::fetch can be called for iterators.

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

The item returned by this WorldQuery For QueryData this will be the item returned by the query. For QueryFilter this will be either (), or a bool indicating whether the entity should be included or a tuple of such things.

type Fetch<'w> = UnsafeWorldCell<'w>

Per archetype/table state used by this WorldQuery to fetch Self::Item

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

This function manually implements subtyping for the query items.

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

Creates a new instance of this fetch.

unsafe fn set_archetype<'w>( _fetch: &mut Self::Fetch<'w>, _state: &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>( _fetch: &mut Self::Fetch<'w>, _state: &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.

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

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 a entity in the current archetype.

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

Adds any component accesses 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 set_access(_state: &mut Self::State, _access: &FilteredAccess<ComponentId>)

Sets available accesses for implementors with dynamic access such as FilteredEntityRef or FilteredEntityMut.

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

impl ReadOnlyQueryData for EntityRef<'_>

SAFETY: access is read only