5c7abb0579
# Objective - Fixes https://github.com/bevyengine/bevy/issues/8239. ## Solution - Replace `OnUpdate` with `run_if(in_state(xxx))`. --- ## Migration Guide - Replace `OnUpdate` with `run_if(in_state(xxx))`. --------- Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
90 lines
2.9 KiB
Rust
90 lines
2.9 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, States)]
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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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#[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_systems(Startup, setup_system)
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.add_systems(
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Update,
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(
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print_text_system,
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transition_to_in_game_system.run_if(in_state(AppState::MainMenu)),
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),
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)
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// Cleanup systems.
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// Pass in the types your system should operate on using the ::<T> (turbofish) syntax
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.add_systems(OnExit(AppState::MainMenu), cleanup_system::<MenuClose>)
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.add_systems(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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