Struct Events 

pub struct Events<T> { /* private fields */ }

The events of type T: a resource of the World with two buffers, the events of the last two updates (DECISIONS #26).

A Schedule updates it at its sync point, at the end of every run: the older buffer is dropped, then the events the systems’ writers sent during the frame are appended in system registration order. Every event has a running id, so a reader that keeps an EventCursor sees every event once, as long as it reads at least once every two updates. The schedule creates the resource for every event type its systems use; World::send_event creates it on the first event.

use pragma_ecs::{EventCursor, Events};

let mut events = Events::<&str>::new();
let mut cursor = EventCursor::default();
events.send("hello")?;
assert_eq!(cursor.read(&events).copied().collect::<Vec<_>>(), ["hello"]);

events.update(); // "hello" is still kept for one more update
events.send("world")?;
assert_eq!(events.len(), 2);
assert_eq!(cursor.read(&events).copied().collect::<Vec<_>>(), ["world"]);

events.update();
events.update(); // both are gone
assert!(events.is_empty());

Implementations

impl<T> Events<T>

pub const fn new() -> Self

No events. Does not allocate.

pub fn send(&mut self, event: T) -> Result<(), EcsError>

Appends event to the current buffer.

Errors

EcsError::OutOfMemory if the buffer cannot grow; the event is dropped.

pub fn update(&mut self)

Drops the events of the previous update and keeps the current ones as the previous. Does not allocate: the two buffers trade places.

pub fn len(&self) -> usize

Number of events kept (both buffers).

pub fn is_empty(&self) -> bool

Whether no event is kept.

pub fn iter(&self) -> EventIter<'_, T>

Every event kept, oldest first.

use pragma_ecs::Events;

let mut events = Events::new();
events.send(1)?;
events.update();
events.send(2)?;
assert_eq!(events.iter().copied().collect::<Vec<_>>(), [1, 2]);

Trait Implementations

impl<T> Debug for Events<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T> Default for Events<T>

fn default() -> Self

Returns the “default value” for a type.