Struct bevy::ecs::change_detection::Ref

pub struct Ref<'w, T>
where T: ?Sized,
{ /* private fields */ }
Expand description

Shared borrow of an entity’s component with access to change detection. Similar to Mut but is immutable and so doesn’t require unique access.

§Examples

These two systems produce the same output.


fn how_many_changed_1(query: Query<(), Changed<MyComponent>>) {
    println!("{} changed", query.iter().count());
}

fn how_many_changed_2(query: Query<Ref<MyComponent>>) {
    println!("{} changed", query.iter().filter(|c| c.is_changed()).count());
}

Implementations§

§

impl<'w, T> Ref<'w, T>
where T: ?Sized,

pub fn into_inner(self) -> &'w T

Returns the reference wrapped by this type. The reference is allowed to outlive self, which makes this method more flexible than simply borrowing self.

pub fn map<U>(self, f: impl FnOnce(&T) -> &U) -> Ref<'w, U>
where U: ?Sized,

Map Ref to a different type using f.

This doesn’t do anything else than call f on the wrapped value. This is equivalent to Mut::map_unchanged.

pub fn new( value: &'w T, added: &'w Tick, changed: &'w Tick, last_run: Tick, this_run: Tick ) -> Ref<'w, T>

Create a new Ref using provided values.

This is an advanced feature, Refs are designed to be created by engine-internal code and consumed by end-user code.

  • value - The value wrapped by Ref.
  • added - A Tick that stores the tick when the wrapped value was created.
  • changed - A Tick that stores the last time the wrapped value was changed.
  • last_run - A Tick, occurring before this_run, which is used as a reference to determine whether the wrapped value is newly added or changed.
  • this_run - A Tick corresponding to the current point in time – “now”.

Trait Implementations§

§

impl<'w, T> AsRef<T> for Ref<'w, T>

§

fn as_ref(&self) -> &T

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

impl<'w, T> Debug for Ref<'w, T>
where T: Debug + ?Sized,

§

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

Formats the value using the given formatter. Read more
§

impl<'w, T> Deref for Ref<'w, T>
where T: ?Sized,

§

type Target = T

The resulting type after dereferencing.
§

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

Dereferences the value.
§

impl<'w, T> DetectChanges for Ref<'w, T>
where T: ?Sized,

§

fn is_added(&self) -> bool

Returns true if this value was added after the system last ran.
§

fn is_changed(&self) -> bool

Returns true if this value was added or mutably dereferenced either since the last time the system ran or, if the system never ran, since the beginning of the program. Read more
§

fn last_changed(&self) -> Tick

Returns the change tick recording the time this data was most recently changed. Read more
§

impl<'w, T> From<Mut<'w, T>> for Ref<'w, T>
where T: ?Sized,

§

fn from(mut_ref: Mut<'w, T>) -> Ref<'w, T>

Converts to this type from the input type.
§

impl<'w, 'a, T> IntoIterator for &'a Ref<'w, T>

§

type Item = <&'a T as IntoIterator>::Item

The type of the elements being iterated over.
§

type IntoIter = <&'a T as IntoIterator>::IntoIter

Which kind of iterator are we turning this into?
§

fn into_iter(self) -> <&'a Ref<'w, T> as IntoIterator>::IntoIter

Creates an iterator from a value. Read more
§

impl<'__w, T> QueryData for Ref<'__w, T>
where T: Component,

SAFETY: Self is the same as Self::ReadOnly

§

type ReadOnly = Ref<'__w, T>

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

impl<'__w, T> WorldQuery for Ref<'__w, T>
where T: Component,

SAFETY: fetch accesses a single component in a readonly way. This is sound because update_component_access and update_archetype_component_access add read access for that component and panic when appropriate. update_component_access adds a With filter for a component. This is sound because matches_component_set returns whether the set contains that component.

§

type Item<'w> = Ref<'w, T>

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> = RefFetch<'w, T>

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

type State = ComponentId

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>(item: Ref<'wlong, T>) -> Ref<'wshort, T>
where 'wlong: 'wshort,

This function manually implements subtyping for the query items.
§

unsafe fn init_fetch<'w>( world: UnsafeWorldCell<'w>, _: &ComponentId, last_run: Tick, this_run: Tick ) -> RefFetch<'w, T>

Creates a new instance of this fetch. Read more
§

const IS_DENSE: bool = _

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.
§

unsafe fn set_archetype<'w>( fetch: &mut RefFetch<'w, T>, component_id: &ComponentId, _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. Read more
§

unsafe fn set_table<'w>( fetch: &mut RefFetch<'w, T>, _: &ComponentId, table: &'w Table )

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

unsafe fn fetch<'w>( fetch: &mut <Ref<'__w, T> as WorldQuery>::Fetch<'w>, entity: Entity, table_row: TableRow ) -> <Ref<'__w, T> as WorldQuery>::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. Read more
§

fn update_component_access( _: &ComponentId, access: &mut FilteredAccess<ComponentId> )

Adds any component accesses used by this WorldQuery to access. Read more
§

fn init_state(world: &mut World) -> ComponentId

Creates and initializes a State for this WorldQuery type.
§

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

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

fn matches_component_set( _: &ComponentId, set_contains_id: &impl Fn(ComponentId) -> bool ) -> bool

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

fn set_access(_state: &mut Self::State, _access: &FilteredAccess<ComponentId>)

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

impl<'__w, T> ReadOnlyQueryData for Ref<'__w, T>
where T: Component,

SAFETY: access is read only

Auto Trait Implementations§

§

impl<'w, T> Freeze for Ref<'w, T>
where T: ?Sized,

§

impl<'w, T> RefUnwindSafe for Ref<'w, T>
where T: RefUnwindSafe + ?Sized,

§

impl<'w, T> Send for Ref<'w, T>
where T: Sync + ?Sized,

§

impl<'w, T> Sync for Ref<'w, T>
where T: Sync + ?Sized,

§

impl<'w, T> Unpin for Ref<'w, T>
where T: ?Sized,

§

impl<'w, T> UnwindSafe for Ref<'w, T>
where T: RefUnwindSafe + ?Sized,

Blanket Implementations§

source§

impl<T> Any for T
where T: 'static + ?Sized,

source§

fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
§

impl<T, U> AsBindGroupShaderType<U> for T
where U: ShaderType, &'a T: for<'a> Into<U>,

§

fn as_bind_group_shader_type(&self, _images: &RenderAssets<GpuImage>) -> U

Return the T ShaderType for self. When used in AsBindGroup derives, it is safe to assume that all images in self exist.
source§

impl<T> Borrow<T> for T
where T: ?Sized,

source§

fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
source§

impl<T> BorrowMut<T> for T
where T: ?Sized,

source§

fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
§

impl<T> Downcast<T> for T

§

fn downcast(&self) -> &T

§

impl<T> Downcast for T
where T: Any,

§

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

Convert Box<dyn Trait> (where Trait: Downcast) to Box<dyn Any>. Box<dyn Any> can then be further downcast into Box<ConcreteType> where ConcreteType implements Trait.
§

fn into_any_rc(self: Rc<T>) -> Rc<dyn Any>

Convert Rc<Trait> (where Trait: Downcast) to Rc<Any>. Rc<Any> can then be further downcast into Rc<ConcreteType> where ConcreteType implements Trait.
§

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

Convert &Trait (where Trait: Downcast) to &Any. This is needed since Rust cannot generate &Any’s vtable from &Trait’s.
§

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

Convert &mut Trait (where Trait: Downcast) to &Any. This is needed since Rust cannot generate &mut Any’s vtable from &mut Trait’s.
§

impl<T> DowncastSync for T
where T: Any + Send + Sync,

§

fn into_any_arc(self: Arc<T>) -> Arc<dyn Any + Send + Sync>

Convert Arc<Trait> (where Trait: Downcast) to Arc<Any>. Arc<Any> can then be further downcast into Arc<ConcreteType> where ConcreteType implements Trait.
source§

impl<T> From<T> for T

source§

fn from(t: T) -> T

Returns the argument unchanged.

§

impl<S> FromSample<S> for S

§

fn from_sample_(s: S) -> S

§

impl<T> Instrument for T

§

fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided Span, returning an Instrumented wrapper. Read more
§

fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current Span, returning an Instrumented wrapper. Read more
source§

impl<T, U> Into<U> for T
where U: From<T>,

source§

fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

source§

impl<T> IntoEither for T

source§

fn into_either(self, into_left: bool) -> Either<Self, Self>

Converts self into a Left variant of Either<Self, Self> if into_left is true. Converts self into a Right variant of Either<Self, Self> otherwise. Read more
source§

fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
where F: FnOnce(&Self) -> bool,

Converts self into a Left variant of Either<Self, Self> if into_left(&self) returns true. Converts self into a Right variant of Either<Self, Self> otherwise. Read more
§

impl<F, T> IntoSample<T> for F
where T: FromSample<F>,

§

fn into_sample(self) -> T

§

impl<T> Pointable for T

§

const ALIGN: usize = _

The alignment of pointer.
§

type Init = T

The type for initializers.
§

unsafe fn init(init: <T as Pointable>::Init) -> usize

Initializes a with the given initializer. Read more
§

unsafe fn deref<'a>(ptr: usize) -> &'a T

Dereferences the given pointer. Read more
§

unsafe fn deref_mut<'a>(ptr: usize) -> &'a mut T

Mutably dereferences the given pointer. Read more
§

unsafe fn drop(ptr: usize)

Drops the object pointed to by the given pointer. Read more
source§

impl<T> Same for T

§

type Output = T

Should always be Self
§

impl<T, U> ToSample<U> for T
where U: FromSample<T>,

§

fn to_sample_(self) -> U

source§

impl<T, U> TryFrom<U> for T
where U: Into<T>,

§

type Error = Infallible

The type returned in the event of a conversion error.
source§

fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
source§

impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

§

type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
source§

fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
§

impl<T> Upcast<T> for T

§

fn upcast(&self) -> Option<&T>

§

impl<V, T> VZip<V> for T
where V: MultiLane<T>,

§

fn vzip(self) -> V

§

impl<T> WithSubscriber for T

§

fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>
where S: Into<Dispatch>,

Attaches the provided Subscriber to this type, returning a WithDispatch wrapper. Read more
§

fn with_current_subscriber(self) -> WithDispatch<Self>

Attaches the current default Subscriber to this type, returning a WithDispatch wrapper. Read more
§

impl<T> ConditionalSend for T
where T: Send,

§

impl<S, T> Duplex<S> for T
where T: FromSample<S> + ToSample<S>,

§

impl<T> Settings for T
where T: 'static + Send + Sync,

§

impl<T> WasmNotSend for T
where T: Send,

§

impl<T> WasmNotSendSync for T
where T: WasmNotSend + WasmNotSync,

§

impl<T> WasmNotSync for T
where T: Sync,