mirror of
https://github.com/bevyengine/bevy
synced 2024-09-20 14:32:06 +00:00
c66c2c7420
# Objective In a few examples, we're specifying a font or font size that is the same as the current default value. Might as well use the default. That'll be one less thing to worry about if we ever need to change the default font size. (wink) In a few others, we were using a value of `25.0` and it didn't seem like it was different for an important reason, so I switched to the default there too. (There are a bunch of examples that use non-default font sizes for various reasons. Not trying address them all here.)
118 lines
3.6 KiB
Rust
118 lines
3.6 KiB
Rust
//! Demonstrates the use of "one-shot systems", which run once when triggered.
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//!
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//! These can be useful to help structure your logic in a push-based fashion,
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//! reducing the overhead of running extremely rarely run systems
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//! and improving schedule flexibility.
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//!
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//! See the [`World::run_system`](World::run_system) or
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//! [`World::run_system_once`](World#method.run_system_once_with)
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//! docs for more details.
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use bevy::{
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ecs::system::{RunSystemOnce, SystemId},
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prelude::*,
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};
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fn main() {
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App::new()
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.add_plugins(DefaultPlugins)
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.add_systems(
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Startup,
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(
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setup_ui,
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setup_with_commands,
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setup_with_world.after(setup_ui), // since we run `system_b` once in world it needs to run after `setup_ui`
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),
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)
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.add_systems(Update, (trigger_system, evaluate_callbacks).chain())
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.run();
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}
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#[derive(Component)]
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struct Callback(SystemId);
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#[derive(Component)]
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struct Triggered;
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#[derive(Component)]
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struct A;
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#[derive(Component)]
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struct B;
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fn setup_with_commands(mut commands: Commands) {
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let system_id = commands.register_one_shot_system(system_a);
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commands.spawn((Callback(system_id), A));
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}
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fn setup_with_world(world: &mut World) {
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// We can run it once manually
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world.run_system_once(system_b);
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// Or with a Callback
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let system_id = world.register_system(system_b);
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world.spawn((Callback(system_id), B));
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}
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/// Tag entities that have callbacks we want to run with the `Triggered` component.
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fn trigger_system(
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mut commands: Commands,
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query_a: Query<Entity, With<A>>,
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query_b: Query<Entity, With<B>>,
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input: Res<ButtonInput<KeyCode>>,
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) {
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if input.just_pressed(KeyCode::KeyA) {
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let entity = query_a.single();
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commands.entity(entity).insert(Triggered);
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}
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if input.just_pressed(KeyCode::KeyB) {
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let entity = query_b.single();
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commands.entity(entity).insert(Triggered);
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}
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}
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/// Runs the systems associated with each `Callback` component if the entity also has a `Triggered` component.
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///
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/// This could be done in an exclusive system rather than using `Commands` if preferred.
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fn evaluate_callbacks(query: Query<(Entity, &Callback), With<Triggered>>, mut commands: Commands) {
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for (entity, callback) in query.iter() {
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commands.run_system(callback.0);
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commands.entity(entity).remove::<Triggered>();
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}
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}
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fn system_a(mut query: Query<&mut Text>) {
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let mut text = query.single_mut();
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text.sections[2].value = String::from("A");
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info!("A: One shot system registered with Commands was triggered");
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}
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fn system_b(mut query: Query<&mut Text>) {
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let mut text = query.single_mut();
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text.sections[2].value = String::from("B");
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info!("B: One shot system registered with World was triggered");
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}
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fn setup_ui(mut commands: Commands) {
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commands.spawn(Camera2dBundle::default());
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commands.spawn(
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TextBundle::from_sections([
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TextSection::new(
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"Press A or B to trigger a one-shot system\n",
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TextStyle::default(),
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),
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TextSection::new("Last Triggered: ", TextStyle::default()),
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TextSection::new(
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"-",
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TextStyle {
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color: bevy::color::palettes::css::ORANGE.into(),
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..default()
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},
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),
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])
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.with_text_justify(JustifyText::Center)
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.with_style(Style {
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align_self: AlignSelf::Center,
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justify_self: JustifySelf::Center,
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..default()
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}),
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);
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}
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