event_split.md

---

title: "`Event` trait split"
pull_requests: [19647]

---

The Event trait was previously used for all types of events: "observer events" with and without targets, and "buffered events" using EventReader and EventWriter.

Buffered events and targeted events have now been split into dedicated BufferedEvent and EntityEvent traits. An event with just the Event trait implemented only supports non-targeted APIs such as global observers and the trigger method.

If an event is used with trigger_targets or an entity observer, make sure you have derived EntityEvent for it.

If an event is used with EventReader or EventWriter, make sure you have derived BufferedEvent for it.