pub struct Changed<T>(_);
Expand description
A filter on a component that only retains results added or mutably dereferenced after the system last ran.
A common use for this filter is avoiding redundant work when values have not changed.
Note that simply mutably dereferencing a component is considered a change (DerefMut
).
Bevy does not compare components to their previous values.
To retain all results without filtering but still check whether they were changed after the
system last ran, use ChangeTrackers<T>
.
Examples
fn print_moving_objects_system(query: Query<&Name, Changed<Transform>>) {
for name in &query {
println!("Entity Moved: {:?}", name);
}
}
Trait Implementations§
§impl<T> WorldQuery for Changed<T>where
T: Component,
impl<T> WorldQuery for Changed<T>where
T: Component,
§type Fetch = ChangedFetch<'w, T>
type Fetch = ChangedFetch<'w, T>
Per archetype/table state used by this
WorldQuery
to fetch Self::Item
§type Item = bool
type Item = bool
The item returned by this
WorldQuery
§type ReadOnly = Changed<T>
type ReadOnly = Changed<T>
The read-only variant of this
WorldQuery
, which satisfies the ReadOnlyWorldQuery
trait.§type State = ComponentId
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
. Read more§fn shrink<'wlong, 'wshort>(
item: <Changed<T> as WorldQuery>::Item<'wlong>
) -> <Changed<T> as WorldQuery>::Item<'wshort>where
'wlong: 'wshort,
fn shrink<'wlong, 'wshort>(
item: <Changed<T> as WorldQuery>::Item<'wlong>
) -> <Changed<T> as WorldQuery>::Item<'wshort>where
'wlong: 'wshort,
This function manually implements subtyping for the query items.
§unsafe fn init_fetch<'w>(
world: &'w World,
_: &ComponentId,
last_change_tick: u32,
change_tick: u32
) -> <Changed<T> as WorldQuery>::Fetch<'w>
unsafe fn init_fetch<'w>(
world: &'w World,
_: &ComponentId,
last_change_tick: u32,
change_tick: u32
) -> <Changed<T> as WorldQuery>::Fetch<'w>
Creates a new instance of this fetch. Read more
§unsafe fn clone_fetch<'w>(
fetch: &<Changed<T> as WorldQuery>::Fetch<'w>
) -> <Changed<T> as WorldQuery>::Fetch<'w>
unsafe fn clone_fetch<'w>(
fetch: &<Changed<T> as WorldQuery>::Fetch<'w>
) -> <Changed<T> as WorldQuery>::Fetch<'w>
While this function can be called for any query, it is always safe to call if
Self: ReadOnlyWorldQuery
holds. Read more§const IS_DENSE: bool = {
match <T::Storage>::STORAGE_TYPE {
StorageType::Table => true,
StorageType::SparseSet => false,
}
}
const IS_DENSE: bool = { match <T::Storage>::STORAGE_TYPE { StorageType::Table => true, StorageType::SparseSet => false, } }
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. Read more§const IS_ARCHETYPAL: bool = false
const IS_ARCHETYPAL: bool = false
Returns true if (and only if) this Fetch relies strictly on archetypes to limit which
components are accessed by the Query. Read more
§unsafe fn set_table<'w>(
fetch: &mut <Changed<T> as WorldQuery>::Fetch<'w>,
_: &ComponentId,
table: &'w Table
)
unsafe fn set_table<'w>(
fetch: &mut <Changed<T> as WorldQuery>::Fetch<'w>,
_: &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 set_archetype<'w>(
fetch: &mut <Changed<T> as WorldQuery>::Fetch<'w>,
component_id: &ComponentId,
_archetype: &'w Archetype,
table: &'w Table
)
unsafe fn set_archetype<'w>(
fetch: &mut <Changed<T> as WorldQuery>::Fetch<'w>,
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 fetch<'w>(
fetch: &mut <Changed<T> as WorldQuery>::Fetch<'w>,
entity: Entity,
table_row: usize
) -> <Changed<T> as WorldQuery>::Item<'w>
unsafe fn fetch<'w>(
fetch: &mut <Changed<T> as WorldQuery>::Fetch<'w>,
entity: Entity,
table_row: usize
) -> <Changed<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§unsafe fn filter_fetch<'w>(
fetch: &mut <Changed<T> as WorldQuery>::Fetch<'w>,
entity: Entity,
table_row: usize
) -> bool
unsafe fn filter_fetch<'w>(
fetch: &mut <Changed<T> as WorldQuery>::Fetch<'w>,
entity: Entity,
table_row: usize
) -> bool
Safety Read more
fn update_component_access(
_: &ComponentId,
access: &mut FilteredAccess<ComponentId>
)
fn update_archetype_component_access(
_: &ComponentId,
archetype: &Archetype,
access: &mut Access<ArchetypeComponentId>
)
fn init_state(world: &mut World) -> ComponentId
fn matches_component_set(
_: &ComponentId,
set_contains_id: &impl Fn(ComponentId) -> bool
) -> bool
impl<T> ReadOnlyWorldQuery for Changed<T>where
T: Component,
SAFETY: read-only access
Auto Trait Implementations§
impl<T> RefUnwindSafe for Changed<T>where
T: RefUnwindSafe,
impl<T> Send for Changed<T>where
T: Send,
impl<T> Sync for Changed<T>where
T: Sync,
impl<T> Unpin for Changed<T>where
T: Unpin,
impl<T> UnwindSafe for Changed<T>where
T: UnwindSafe,
Blanket Implementations§
§impl<T, U> AsBindGroupShaderType<U> for Twhere
U: ShaderType,
&'a T: for<'a> Into<U>,
impl<T, U> AsBindGroupShaderType<U> for Twhere
U: ShaderType,
&'a T: for<'a> Into<U>,
§fn as_bind_group_shader_type(&self, _images: &RenderAssets<Image>) -> U
fn as_bind_group_shader_type(&self, _images: &RenderAssets<Image>) -> U
Return the
T
ShaderType
for self
. When used in AsBindGroup
derives, it is safe to assume that all images in self
exist. Read more§impl<T> Downcast for Twhere
T: Any,
impl<T> Downcast for Twhere
T: Any,
§fn into_any(self: Box<T, Global>) -> Box<dyn Any + 'static, Global>
fn into_any(self: Box<T, Global>) -> Box<dyn Any + 'static, Global>
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
. Read more§fn into_any_rc(self: Rc<T>) -> Rc<dyn Any + 'static>
fn into_any_rc(self: Rc<T>) -> Rc<dyn Any + 'static>
Convert
Rc<Trait>
(where Trait: Downcast
) to Rc<Any>
. Rc<Any>
can then be
further downcast
into Rc<ConcreteType>
where ConcreteType
implements Trait
. Read more§fn as_any(&self) -> &(dyn Any + 'static)
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. Read more§fn as_any_mut(&mut self) -> &mut (dyn Any + 'static)
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. Read more