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*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>
77 lines
2.3 KiB
Rust
77 lines
2.3 KiB
Rust
//! Illustrates how `Timer`s can be used both as resources and components.
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use bevy::{log::info, prelude::*};
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fn main() {
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App::new()
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.add_plugins(DefaultPlugins)
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.init_resource::<Countdown>()
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.add_startup_system(setup)
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.add_system(countdown)
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.add_system(print_when_completed)
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.run();
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}
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#[derive(Component, Deref, DerefMut)]
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pub struct PrintOnCompletionTimer(Timer);
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#[derive(Resource)]
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pub struct Countdown {
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pub percent_trigger: Timer,
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pub main_timer: Timer,
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}
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impl Countdown {
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pub fn new() -> Self {
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Self {
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percent_trigger: Timer::from_seconds(4.0, true),
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main_timer: Timer::from_seconds(20.0, false),
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}
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}
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}
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impl Default for Countdown {
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fn default() -> Self {
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Self::new()
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}
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}
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fn setup(mut commands: Commands) {
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// Add an entity to the world with a timer
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commands
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.spawn()
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.insert(PrintOnCompletionTimer(Timer::from_seconds(5.0, false)));
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}
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/// This system ticks all the `Timer` components on entities within the scene
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/// using bevy's `Time` resource to get the delta between each update.
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fn print_when_completed(time: Res<Time>, mut query: Query<&mut PrintOnCompletionTimer>) {
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for mut timer in &mut query {
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if timer.tick(time.delta()).just_finished() {
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info!("Entity timer just finished");
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}
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}
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}
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/// This system controls ticking the timer within the countdown resource and
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/// handling its state.
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fn countdown(time: Res<Time>, mut countdown: ResMut<Countdown>) {
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countdown.main_timer.tick(time.delta());
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// The API encourages this kind of timer state checking (if you're only checking for one value)
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// Additionally, `finished()` would accomplish the same thing as `just_finished` due to the
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// timer being repeating, however this makes more sense visually.
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if countdown.percent_trigger.tick(time.delta()).just_finished() {
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if !countdown.main_timer.finished() {
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// Print the percent complete the main timer is.
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info!(
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"Timer is {:0.0}% complete!",
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countdown.main_timer.percent() * 100.0
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);
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} else {
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// The timer has finished so we pause the percent output timer
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countdown.percent_trigger.pause();
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info!("Paused percent trigger timer");
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}
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}
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}
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