Struct bevy_ecs::change_detection::Ref
source · pub struct Ref<'w, 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§
source§impl<'w, T: ?Sized> Ref<'w, T>
impl<'w, T: ?Sized> Ref<'w, T>
sourcepub fn into_inner(self) -> &'w T
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
.
sourcepub fn map<U: ?Sized>(self, f: impl FnOnce(&T) -> &U) -> Ref<'w, U>
pub fn map<U: ?Sized>(self, f: impl FnOnce(&T) -> &U) -> Ref<'w, U>
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
.
sourcepub fn new(
value: &'w T,
added: &'w Tick,
changed: &'w Tick,
last_run: Tick,
this_run: Tick
) -> Ref<'w, T>
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, Ref
s are designed to be created by
engine-internal code and consumed by end-user code.
value
- The value wrapped byRef
.added
- ATick
that stores the tick when the wrapped value was created.changed
- ATick
that stores the last time the wrapped value was changed.last_run
- ATick
, occurring beforethis_run
, which is used as a reference to determine whether the wrapped value is newly added or changed.this_run
- ATick
corresponding to the current point in time – “now”.
Trait Implementations§
source§impl<'w, T: ?Sized> DetectChanges for Ref<'w, T>
impl<'w, T: ?Sized> DetectChanges for Ref<'w, T>
source§fn is_changed(&self) -> bool
fn is_changed(&self) -> bool
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 moresource§fn last_changed(&self) -> Tick
fn last_changed(&self) -> Tick
source§impl<'w, 'a, T> IntoIterator for &'a Ref<'w, T>where
&'a T: IntoIterator,
impl<'w, 'a, T> IntoIterator for &'a Ref<'w, T>where
&'a T: IntoIterator,
source§impl<'__w, T: Component> QueryData for Ref<'__w, T>
impl<'__w, T: Component> QueryData for Ref<'__w, T>
SAFETY: Self
is the same as Self::ReadOnly
§type ReadOnly = Ref<'__w, T>
type ReadOnly = Ref<'__w, T>
QueryData
, which satisfies the ReadOnlyQueryData
trait.source§impl<'__w, T: Component> WorldQuery for Ref<'__w, T>
impl<'__w, T: Component> WorldQuery for Ref<'__w, T>
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>
type Item<'w> = Ref<'w, T>
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>
type Fetch<'w> = RefFetch<'w, T>
WorldQuery
to fetch Self::Item
§type State = ComponentId
type State = ComponentId
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
.source§fn shrink<'wlong: 'wshort, 'wshort>(item: Ref<'wlong, T>) -> Ref<'wshort, T>
fn shrink<'wlong: 'wshort, 'wshort>(item: Ref<'wlong, T>) -> Ref<'wshort, T>
source§unsafe fn init_fetch<'w>(
world: UnsafeWorldCell<'w>,
component_id: &ComponentId,
last_run: Tick,
this_run: Tick
) -> RefFetch<'w, T>
unsafe fn init_fetch<'w>( world: UnsafeWorldCell<'w>, component_id: &ComponentId, last_run: Tick, this_run: Tick ) -> RefFetch<'w, T>
source§const IS_DENSE: bool = _
const IS_DENSE: bool = _
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.source§unsafe fn set_archetype<'w>(
fetch: &mut RefFetch<'w, T>,
component_id: &ComponentId,
_archetype: &'w Archetype,
table: &'w Table
)
unsafe fn set_archetype<'w>( fetch: &mut RefFetch<'w, T>, component_id: &ComponentId, _archetype: &'w Archetype, table: &'w Table )
Archetype
. This will always be called on
archetypes that match this WorldQuery
. Read moresource§unsafe fn set_table<'w>(
fetch: &mut RefFetch<'w, T>,
component_id: &ComponentId,
table: &'w Table
)
unsafe fn set_table<'w>( fetch: &mut RefFetch<'w, T>, component_id: &ComponentId, table: &'w Table )
Table
. This will always be called on tables
that match this WorldQuery
. Read moresource§unsafe fn fetch<'w>(
fetch: &mut Self::Fetch<'w>,
entity: Entity,
table_row: TableRow
) -> Self::Item<'w>
unsafe fn fetch<'w>( fetch: &mut Self::Fetch<'w>, entity: Entity, table_row: TableRow ) -> Self::Item<'w>
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 moresource§fn update_component_access(
component_id: &ComponentId,
access: &mut FilteredAccess<ComponentId>
)
fn update_component_access( component_id: &ComponentId, access: &mut FilteredAccess<ComponentId> )
source§fn init_state(world: &mut World) -> ComponentId
fn init_state(world: &mut World) -> ComponentId
State
for this WorldQuery
type.source§fn matches_component_set(
state: &ComponentId,
set_contains_id: &impl Fn(ComponentId) -> bool
) -> bool
fn matches_component_set( state: &ComponentId, set_contains_id: &impl Fn(ComponentId) -> bool ) -> bool
source§fn set_access(_state: &mut Self::State, _access: &FilteredAccess<ComponentId>)
fn set_access(_state: &mut Self::State, _access: &FilteredAccess<ComponentId>)
FilteredEntityRef
or FilteredEntityMut
. Read moreimpl<'__w, T: Component> ReadOnlyQueryData for Ref<'__w, T>
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>
impl<'w, T> Sync for Ref<'w, T>
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> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere
T: ?Sized,
source§fn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
source§impl<T> Downcast for Twhere
T: Any,
impl<T> Downcast for Twhere
T: Any,
source§fn into_any(self: Box<T>) -> Box<dyn Any>
fn into_any(self: Box<T>) -> Box<dyn Any>
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
.source§fn into_any_rc(self: Rc<T>) -> Rc<dyn Any>
fn into_any_rc(self: Rc<T>) -> Rc<dyn Any>
Rc<Trait>
(where Trait: Downcast
) to Rc<Any>
. Rc<Any>
can then be
further downcast
into Rc<ConcreteType>
where ConcreteType
implements Trait
.source§fn as_any(&self) -> &(dyn Any + 'static)
fn as_any(&self) -> &(dyn Any + 'static)
&Trait
(where Trait: Downcast
) to &Any
. This is needed since Rust cannot
generate &Any
’s vtable from &Trait
’s.source§fn as_any_mut(&mut self) -> &mut (dyn Any + 'static)
fn as_any_mut(&mut self) -> &mut (dyn Any + 'static)
&mut Trait
(where Trait: Downcast
) to &Any
. This is needed since Rust cannot
generate &mut Any
’s vtable from &mut Trait
’s.