Struct EcsEventReader 

pub struct EcsEventReader<'w, 's, E: Event> { /* private fields */ }

ECS system parameter for reading events of type E.

Wraps a reference to the Events<E> resource and a cursor stored in the system’s cached state. Each system using EcsEventReader<E> gets its own cursor, so multiple systems can independently consume the same events.

Example

fn damage_system(mut reader: EcsEventReader<DamageEvent>) {
    for event in reader.read() {
        println!("Damage: {}", event.amount);
    }
}

Frame Lifecycle

Events written during frame N become readable after Events::update() is called. The cursor automatically resets when the read buffer changes.

Implementations

impl<'w, 's, E: Event> EcsEventReader<'w, 's, E>

pub fn read(&mut self) -> impl Iterator<Item = &'w E>

Returns an iterator over unread events since this system last ran.

Advances the cursor so that the next call to read() (in a subsequent system run) returns only newly available events.

pub fn is_empty(&self) -> bool

Returns true if there are no unread events for this system.

pub fn len(&self) -> usize

Returns the number of unread events for this system.

Trait Implementations

impl<E: Event> SystemParam for EcsEventReader<'_, '_, E>

type State = EcsEventReaderState<E>

The cached state for this parameter.

type Item<'w, 's> = EcsEventReader<'w, 's, E>

The type of value this parameter produces.

fn update_access(_state: &Self::State, access: &mut Access)

Updates the access pattern for this parameter.

fn get_param<'w, 's>( state: &'s mut Self::State, world: &'w World, ) -> Self::Item<'w, 's>

Extracts the parameter value from the World.

fn get_param_mut<'w, 's>( state: &'s mut Self::State, world: &'w mut World, ) -> Self::Item<'w, 's>

Extracts the parameter value from a mutable World reference.

impl<E: Event> ReadOnlySystemParam for EcsEventReader<'_, '_, E>

EcsEventReader<E> is read-only.