mirror of
https://github.com/bevyengine/bevy
synced 2024-11-10 07:04:33 +00:00
0a9c469d19
# Objective Fixes #7632. As discussed in #7634, it can be quite challenging for users to intuit the mental model of how states now work. ## Solution Rather than change the behavior of the `OnUpdate` system set, instead work on making sure it's easy to understand what's going on. Two things have been done: 1. Remove the `.on_update` method from our bevy of system building traits. This was special-cased and made states feel much more magical than they need to. 2. Improve the docs for the `OnUpdate` system set.
95 lines
3.1 KiB
Rust
95 lines
3.1 KiB
Rust
//! Generic types allow us to reuse logic across many related systems,
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//! allowing us to specialize our function's behavior based on which type (or types) are passed in.
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//!
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//! This is commonly useful for working on related components or resources,
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//! where we want to have unique types for querying purposes but want them all to work the same way.
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//! This is particularly powerful when combined with user-defined traits to add more functionality to these related types.
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//! Remember to insert a specialized copy of the system into the schedule for each type that you want to operate on!
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//!
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//! For more advice on working with generic types in Rust, check out <https://doc.rust-lang.org/book/ch10-01-syntax.html>
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//! or <https://doc.rust-lang.org/rust-by-example/generics.html>
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use bevy::prelude::*;
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#[derive(Debug, Default, Clone, Copy, Eq, PartialEq, Hash)]
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enum AppState {
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#[default]
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MainMenu,
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InGame,
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}
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impl States for AppState {
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type Iter = std::array::IntoIter<AppState, 2>;
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fn variants() -> Self::Iter {
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[AppState::MainMenu, AppState::InGame].into_iter()
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}
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}
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#[derive(Component)]
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struct TextToPrint(String);
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#[derive(Component, Deref, DerefMut)]
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struct PrinterTick(Timer);
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#[derive(Component)]
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struct MenuClose;
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#[derive(Component)]
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struct LevelUnload;
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fn main() {
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App::new()
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.add_plugins(DefaultPlugins)
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.add_state::<AppState>()
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.add_startup_system(setup_system)
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.add_system(print_text_system)
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.add_system(transition_to_in_game_system.in_set(OnUpdate(AppState::MainMenu)))
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// add the cleanup systems
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.add_system_to_schedule(
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OnExit(AppState::MainMenu),
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// Pass in the types your system should operate on using the ::<T> (turbofish) syntax
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cleanup_system::<MenuClose>,
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)
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.add_system_to_schedule(OnExit(AppState::InGame), cleanup_system::<LevelUnload>)
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.run();
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}
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fn setup_system(mut commands: Commands) {
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commands.spawn((
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PrinterTick(Timer::from_seconds(1.0, TimerMode::Repeating)),
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TextToPrint("I will print until you press space.".to_string()),
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MenuClose,
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));
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commands.spawn((
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PrinterTick(Timer::from_seconds(1.0, TimerMode::Repeating)),
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TextToPrint("I will always print".to_string()),
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LevelUnload,
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));
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}
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fn print_text_system(time: Res<Time>, mut query: Query<(&mut PrinterTick, &TextToPrint)>) {
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for (mut timer, text) in &mut query {
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if timer.tick(time.delta()).just_finished() {
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info!("{}", text.0);
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}
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}
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}
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fn transition_to_in_game_system(
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mut next_state: ResMut<NextState<AppState>>,
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keyboard_input: Res<Input<KeyCode>>,
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) {
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if keyboard_input.pressed(KeyCode::Space) {
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next_state.set(AppState::InGame);
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}
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}
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// Type arguments on functions come after the function name, but before ordinary arguments.
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// Here, the `Component` trait is a trait bound on T, our generic type
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fn cleanup_system<T: Component>(mut commands: Commands, query: Query<Entity, With<T>>) {
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for e in &query {
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commands.entity(e).despawn_recursive();
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}
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}
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