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
) -> impl DoubleEndedIterator<Item = &E> + ExactSizeIterator<Item = &E>
pub fn iter(
&mut self
) -> impl DoubleEndedIterator<Item = &E> + ExactSizeIterator<Item = &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
) -> impl DoubleEndedIterator<Item = (&E, EventId<E>)> + ExactSizeIterator<Item = (&E, EventId<E>)>
pub fn iter_with_id(
&mut self
) -> impl DoubleEndedIterator<Item = (&E, EventId<E>)> + ExactSizeIterator<Item = (&E, EventId<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
Determines if no events are available to be read without consuming any.
If you need to consume the iterator you can use EventReader::clear
.
Example
The following example shows a common pattern of this function in conjunction with clear
to avoid leaking events to the next schedule iteration while also checking if it was emitted.
struct CollisionEvent;
fn play_collision_sound(events: EventReader<CollisionEvent>) {
if !events.is_empty() {
events.clear();
// Play a sound
}
}
sourcepub fn clear(self)
pub fn clear(self)
Consumes the iterator.
This means all currently available events will be removed before the next frame. This is useful when multiple events are sent in a single frame and you want to react to one or more events without needing to know how many were sent. In those situations you generally want to consume those events to make sure they don’t appear in the next frame.
For more information see EventReader::is_empty()
.
Trait Implementations§
source§impl<'w, 's, E: Event> SystemParam for EventReader<'w, 's, E>
impl<'w, 's, E: Event> SystemParam for EventReader<'w, 's, E>
type Fetch = FetchState<(<Local<'s, ManualEventReader<E>> as SystemParam>::Fetch, <Res<'w, Events<E>> as SystemParam>::Fetch), E>
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
. Read moresource§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
. Read moresource§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. Read moresource§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. Read more