Struct InstanceRef 

pub struct InstanceRef<'a, T>(/* private fields */)
where
    T: Component;

A QueryData item which represents a reference to an Instance<T> and its associated Component.

This is analogous to a (Instance<T>, &T) query.

Usage

If a Kind is also a component, it is often convenient to access the instance and component data together. This type is designed to make these queries more ergonomic.

You may use this type as either a Query parameter, or access it from an EntityRef.

Example

#[derive(Component)]
struct Apple {
    freshness: f32,
}

impl Apple {
    fn is_fresh(&self) -> bool {
        self.freshness >= 0.5
    }
}

// Query Access:
fn fresh_apples(query: Query<InstanceRef<Apple>>) -> Vec<Instance<Apple>> {
    query.iter()
        .filter_map(|apple| apple.is_fresh().then_some(apple.instance()))
        .collect()
}

// Entity Access:
fn fresh_apples_world<'a>(world: &'a World) -> Vec<InstanceRef<'a, Apple>> {
   world.try_query::<EntityRef>()
        .unwrap()
        .iter(&world)
        .filter_map(|entity| InstanceRef::from_entity(entity))
        .collect()
}

Implementations

impl<'a, T> InstanceRef<'a, T>

where T: Component,

pub fn from_entity(entity: EntityRef<'a>) -> Option<InstanceRef<'a, T>>

Creates a new InstanceRef<T> from an EntityRef if it contains a given Component of type T.

pub unsafe fn from_entity_unchecked(entity: EntityRef<'a>) -> InstanceRef<'a, T>

Creates a new InstanceRef<T> from EntityRef without any validation.

Safety

Assumes entity is a valid instance of kind T.

Trait Implementations

impl<T> AsRef<Instance<T>> for InstanceRef<'_, T>

where T: Component,

fn as_ref(&self) -> &Instance<T>

Converts this type into a shared reference of the (usually inferred) input type.

impl<T> AsRef<T> for InstanceRef<'_, T>

where T: Component,

fn as_ref(&self) -> &T

Converts this type into a shared reference of the (usually inferred) input type.

impl<T> Clone for InstanceRef<'_, T>

where T: Component,

fn clone(&self) -> InstanceRef<'_, T>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<T> ContainsInstance<T> for InstanceRef<'_, T>

where T: Component,

fn instance(&self) -> Instance<T>

Returns the associated Instance<T>.

fn entity(&self) -> Entity

Returns the Entity of the associated Instance<T>.

impl<T> Deref for InstanceRef<'_, T>

where T: Component,

type Target = T

The resulting type after dereferencing.

fn deref(&self) -> &<InstanceRef<'_, T> as Deref>::Target

Dereferences the value.

impl<T> From<&InstanceRef<'_, T>> for Instance<T>

where T: Component,

fn from(item: &InstanceRef<'_, T>) -> Instance<T>

Converts to this type from the input type.

impl<T> From<InstanceRef<'_, T>> for Instance<T>

where T: Component,

fn from(item: InstanceRef<'_, T>) -> Instance<T>

Converts to this type from the input type.

impl<T> PartialEq for InstanceRef<'_, T>

where T: Component,

fn eq(&self, other: &InstanceRef<'_, T>) -> 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<T> QueryData for InstanceRef<'_, T>

where T: Component,

const IS_READ_ONLY: bool = true

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

const IS_ARCHETYPAL: bool = <&'static T as QueryData>::IS_ARCHETYPAL

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

type ReadOnly = InstanceRef<'_, T>

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

type Item<'w, 's> = InstanceRef<'w, T>

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, 's>( item: <InstanceRef<'_, T> as QueryData>::Item<'wlong, 's>, ) -> <InstanceRef<'_, T> as QueryData>::Item<'wshort, 's>

where 'wlong: 'wshort,

This function manually implements subtyping for the query items.

unsafe fn fetch<'w, 's>( state: &'s <InstanceRef<'_, T> as WorldQuery>::State, fetch: &mut <InstanceRef<'_, T> as WorldQuery>::Fetch<'w>, entity: Entity, table_row: TableRow, ) -> Option<<InstanceRef<'_, T> as QueryData>::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: &<InstanceRef<'_, T> as WorldQuery>::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<T> WorldQuery for InstanceRef<'_, T>

where T: Component,

const IS_DENSE: bool = <(Instance<T>, &T) as WorldQuery>::IS_DENSE

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

type Fetch<'w> = <(Instance<T>, &'static T) as WorldQuery>::Fetch<'w>

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

type State = <(Instance<T>, &'static T) as WorldQuery>::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>( fetch: <InstanceRef<'_, T> as WorldQuery>::Fetch<'wlong>, ) -> <InstanceRef<'_, T> as WorldQuery>::Fetch<'wshort>

where 'wlong: 'wshort,

This function manually implements subtyping for the query fetches.

unsafe fn init_fetch<'w>( world: UnsafeWorldCell<'w>, state: &<InstanceRef<'_, T> as WorldQuery>::State, last_run: Tick, this_run: Tick, ) -> <InstanceRef<'_, T> as WorldQuery>::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>( fetch: &mut <InstanceRef<'_, T> as WorldQuery>::Fetch<'w>, state: &<InstanceRef<'_, T> as WorldQuery>::State, archetype: &'w Archetype, table: &'w 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 <InstanceRef<'_, T> as WorldQuery>::Fetch<'w>, state: &<InstanceRef<'_, T> as WorldQuery>::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: &<InstanceRef<'_, T> as WorldQuery>::State, access: &mut FilteredAccess, )

Adds any component accesses used by this WorldQuery to access.

fn init_state(world: &mut World) -> <InstanceRef<'_, T> as WorldQuery>::State

Creates and initializes a State for this WorldQuery type.

fn get_state( components: &Components, ) -> Option<<InstanceRef<'_, T> as WorldQuery>::State>

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

fn matches_component_set( state: &<InstanceRef<'_, T> as WorldQuery>::State, set_contains_id: &impl Fn(ComponentId) -> bool, ) -> bool

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

impl<T> Copy for InstanceRef<'_, T>

where T: Component,

impl<T> Eq for InstanceRef<'_, T>

where T: Component,

impl<T> ReadOnlyQueryData for InstanceRef<'_, T>

where T: Component,