Struct bevy_ecs::event::EventReader
source · pub struct EventReader<'w, 's, E: Event> { /* private fields */ }
Expand description
Reads events of type T
in order and tracks which events have already been read.
Implementations§
source§impl<'w, 's, E: Event> EventReader<'w, 's, E>
impl<'w, 's, E: Event> EventReader<'w, 's, E>
sourcepub fn iter(&mut self) -> ManualEventIterator<'_, E> ⓘ
pub fn iter(&mut self) -> ManualEventIterator<'_, E> ⓘ
Iterates over the events this EventReader
has not seen yet. This updates the
EventReader
’s event counter, which means subsequent event reads will not include events
that happened before now.
sourcepub fn iter_with_id(&mut self) -> ManualEventIteratorWithId<'_, E> ⓘ
pub fn iter_with_id(&mut self) -> ManualEventIteratorWithId<'_, E> ⓘ
sourcepub fn len(&self) -> usize
pub fn len(&self) -> usize
Determines the number of events available to be read from this EventReader
without consuming any.
sourcepub fn is_empty(&self) -> bool
pub fn is_empty(&self) -> bool
Returns true
if there are no events available to read.
Example
The following example shows a useful pattern where some behaviour is triggered if new events are available.
EventReader::clear()
is used so the same events don’t re-trigger the behaviour the next time the system runs.
struct CollisionEvent;
fn play_collision_sound(mut events: EventReader<CollisionEvent>) {
if !events.is_empty() {
events.clear();
// Play a sound
}
}
sourcepub fn clear(&mut self)
pub fn clear(&mut self)
Consumes all available events.
This means these events will not appear in calls to EventReader::iter()
or
EventReader::iter_with_id()
and EventReader::is_empty()
will return true
.
For usage, see EventReader::is_empty()
.
Trait Implementations§
source§impl<'a, 'w, 's, E: Event> IntoIterator for &'a mut EventReader<'w, 's, E>
impl<'a, 'w, 's, E: Event> IntoIterator for &'a mut EventReader<'w, 's, E>
source§impl<E: Event> SystemParam for EventReader<'_, '_, E>
impl<E: Event> SystemParam for EventReader<'_, '_, E>
§type Item<'w, 's> = EventReader<'w, 's, E>
type Item<'w, 's> = EventReader<'w, 's, E>
Self
, instantiated with new lifetimes. Read moresource§fn init_state(world: &mut World, system_meta: &mut SystemMeta) -> Self::State
fn init_state(world: &mut World, system_meta: &mut SystemMeta) -> Self::State
World
access used by this SystemParam
and creates a new instance of this param’s State
.source§fn new_archetype(
state: &mut Self::State,
archetype: &Archetype,
system_meta: &mut SystemMeta
)
fn new_archetype( state: &mut Self::State, archetype: &Archetype, system_meta: &mut SystemMeta )
Archetype
, registers the components accessed by this SystemParam
(if applicable).source§fn apply(state: &mut Self::State, system_meta: &SystemMeta, world: &mut World)
fn apply(state: &mut Self::State, system_meta: &SystemMeta, world: &mut World)
SystemParam
’s state.
This is used to apply Commands
during apply_system_buffers
.impl<'w, 's, E: Event> ReadOnlySystemParam for EventReader<'w, 's, E>where Local<'s, ManualEventReader<E>>: ReadOnlySystemParam, Res<'w, Events<E>>: ReadOnlySystemParam,
Auto Trait Implementations§
impl<'w, 's, E> RefUnwindSafe for EventReader<'w, 's, E>where E: RefUnwindSafe,
impl<'w, 's, E> Send for EventReader<'w, 's, E>
impl<'w, 's, E> Sync for EventReader<'w, 's, E>
impl<'w, 's, E> Unpin for EventReader<'w, 's, E>
impl<'w, 's, E> !UnwindSafe for EventReader<'w, 's, E>
Blanket Implementations§
source§impl<T> Downcast for Twhere
T: Any,
impl<T> Downcast for Twhere T: Any,
source§fn into_any(self: Box<T, Global>) -> Box<dyn Any + 'static, Global>
fn into_any(self: Box<T, Global>) -> Box<dyn Any + 'static, Global>
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 + 'static>
fn into_any_rc(self: Rc<T>) -> Rc<dyn Any + 'static>
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.