89cbc78d3d
# Objective Be consistent with `Resource`s and `Components` and have `Event` types be more self-documenting. Although not susceptible to accidentally using a function instead of a value due to `Event`s only being initialized by their type, much of the same reasoning for removing the blanket impl on `Resource` also applies here. * Not immediately obvious if a type is intended to be an event * Prevent invisible conflicts if the same third-party or primitive types are used as events * Allows for further extensions (e.g. opt-in warning for missed events) ## Solution Remove the blanket impl for the `Event` trait. Add a derive macro for it. --- ## Changelog - `Event` is no longer implemented for all applicable types. Add the `#[derive(Event)]` macro for events. ## Migration Guide * Add the `#[derive(Event)]` macro for events. Third-party types used as events should be wrapped in a newtype.
64 lines
1.5 KiB
Rust
64 lines
1.5 KiB
Rust
//! This example creates a new event, a system that triggers the event once per second,
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//! and a system that prints a message whenever the event is received.
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use bevy::prelude::*;
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fn main() {
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App::new()
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.add_plugins(DefaultPlugins)
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.add_event::<MyEvent>()
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.add_event::<PlaySound>()
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.init_resource::<EventTriggerState>()
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.add_systems(Update, (event_trigger, event_listener, sound_player))
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.run();
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}
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#[derive(Event)]
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struct MyEvent {
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pub message: String,
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}
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#[derive(Event, Default)]
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struct PlaySound;
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#[derive(Resource)]
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struct EventTriggerState {
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event_timer: Timer,
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}
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impl Default for EventTriggerState {
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fn default() -> Self {
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EventTriggerState {
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event_timer: Timer::from_seconds(1.0, TimerMode::Repeating),
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}
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}
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}
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// sends MyEvent and PlaySound every second
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fn event_trigger(
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time: Res<Time>,
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mut state: ResMut<EventTriggerState>,
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mut my_events: EventWriter<MyEvent>,
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mut play_sound_events: EventWriter<PlaySound>,
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) {
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if state.event_timer.tick(time.delta()).finished() {
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my_events.send(MyEvent {
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message: "MyEvent just happened!".to_string(),
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});
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play_sound_events.send_default();
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}
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}
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// prints events as they come in
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fn event_listener(mut events: EventReader<MyEvent>) {
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for my_event in events.iter() {
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info!("{}", my_event.message);
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}
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}
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fn sound_player(mut play_sound_events: EventReader<PlaySound>) {
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for _ in play_sound_events.iter() {
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info!("Playing a sound");
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}
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}
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