992681b59b
*This PR description is an edited copy of #5007, written by @alice-i-cecile.* # Objective Follow-up to https://github.com/bevyengine/bevy/pull/2254. The `Resource` trait currently has a blanket implementation for all types that meet its bounds. While ergonomic, this results in several drawbacks: * it is possible to make confusing, silent mistakes such as inserting a function pointer (Foo) rather than a value (Foo::Bar) as a resource * it is challenging to discover if a type is intended to be used as a resource * we cannot later add customization options (see the [RFC](https://github.com/bevyengine/rfcs/blob/main/rfcs/27-derive-component.md) for the equivalent choice for Component). * dependencies can use the same Rust type as a resource in invisibly conflicting ways * raw Rust types used as resources cannot preserve privacy appropriately, as anyone able to access that type can read and write to internal values * we cannot capture a definitive list of possible resources to display to users in an editor ## Notes to reviewers * Review this commit-by-commit; there's effectively no back-tracking and there's a lot of churn in some of these commits. *ira: My commits are not as well organized :')* * I've relaxed the bound on Local to Send + Sync + 'static: I don't think these concerns apply there, so this can keep things simple. Storing e.g. a u32 in a Local is fine, because there's a variable name attached explaining what it does. * I think this is a bad place for the Resource trait to live, but I've left it in place to make reviewing easier. IMO that's best tackled with https://github.com/bevyengine/bevy/issues/4981. ## Changelog `Resource` is no longer automatically implemented for all matching types. Instead, use the new `#[derive(Resource)]` macro. ## Migration Guide Add `#[derive(Resource)]` to all types you are using as a resource. If you are using a third party type as a resource, wrap it in a tuple struct to bypass orphan rules. Consider deriving `Deref` and `DerefMut` to improve ergonomics. `ClearColor` no longer implements `Component`. Using `ClearColor` as a component in 0.8 did nothing. Use the `ClearColorConfig` in the `Camera3d` and `Camera2d` components instead. Co-authored-by: Alice <alice.i.cecile@gmail.com> Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com> Co-authored-by: devil-ira <justthecooldude@gmail.com> Co-authored-by: Carter Anderson <mcanders1@gmail.com>
65 lines
1.5 KiB
Rust
65 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_system(event_trigger)
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.add_system(event_listener)
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.add_system(sound_player)
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.run();
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}
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struct MyEvent {
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pub message: String,
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}
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#[derive(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, true),
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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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