diff --git a/examples/ecs/one_shot_systems.rs b/examples/ecs/one_shot_systems.rs index 2cf3a02b5c..63c2b43cdd 100644 --- a/examples/ecs/one_shot_systems.rs +++ b/examples/ecs/one_shot_systems.rs @@ -15,45 +15,114 @@ use bevy::{ fn main() { App::new() - .add_systems(Startup, (count_entities, setup)) - .add_systems(PostUpdate, count_entities) - .add_systems(Update, evaluate_callbacks) + .add_plugins(DefaultPlugins) + .add_systems( + Startup, + ( + setup_ui, + setup_with_commands, + setup_with_world.after(setup_ui), // since we run `system_b` once in world it needs to run after `setup_ui` + ), + ) + .add_systems(Update, (trigger_system, evaluate_callbacks).chain()) .run(); } -// Any ordinary system can be run via commands.run_system or world.run_system. -fn count_entities(all_entities: Query<()>) { - dbg!(all_entities.iter().count()); -} - #[derive(Component)] struct Callback(SystemId); #[derive(Component)] struct Triggered; -fn setup(world: &mut World) { - let button_pressed_id = world.register_system(button_pressed); - world.spawn((Callback(button_pressed_id), Triggered)); - // This entity does not have a Triggered component, so its callback won't run. - let slider_toggled_id = world.register_system(slider_toggled); - world.spawn(Callback(slider_toggled_id)); - world.run_system_once(count_entities); +#[derive(Component)] +struct A; +#[derive(Component)] +struct B; + +fn setup_with_commands(mut commands: Commands) { + let system_id = commands.register_one_shot_system(system_a); + commands.spawn((Callback(system_id), A)); } -fn button_pressed() { - println!("A button was pressed!"); +fn setup_with_world(world: &mut World) { + // We can run it once manually + world.run_system_once(system_b); + // Or with a Callback + let system_id = world.register_system(system_b); + world.spawn((Callback(system_id), B)); } -fn slider_toggled() { - println!("A slider was toggled!"); -} - -/// Runs the systems associated with each `Callback` component if the entity also has a Triggered component. -/// -/// This could be done in an exclusive system rather than using `Commands` if preferred. -fn evaluate_callbacks(query: Query<&Callback, With>, mut commands: Commands) { - for callback in query.iter() { - commands.run_system(callback.0); +/// Tag entities that have callbacks we want to run with the `Triggered` component. +fn trigger_system( + mut commands: Commands, + query_a: Query>, + query_b: Query>, + input: Res>, +) { + if input.just_pressed(KeyCode::KeyA) { + let entity = query_a.single(); + commands.entity(entity).insert(Triggered); + } + if input.just_pressed(KeyCode::KeyB) { + let entity = query_b.single(); + commands.entity(entity).insert(Triggered); } } + +/// Runs the systems associated with each `Callback` component if the entity also has a `Triggered` component. +/// +/// This could be done in an exclusive system rather than using `Commands` if preferred. +fn evaluate_callbacks(query: Query<(Entity, &Callback), With>, mut commands: Commands) { + for (entity, callback) in query.iter() { + commands.run_system(callback.0); + commands.entity(entity).remove::(); + } +} + +fn system_a(mut query: Query<&mut Text>) { + let mut text = query.single_mut(); + text.sections[2].value = String::from("A"); + info!("A: One shot system registered with Commands was triggered"); +} + +fn system_b(mut query: Query<&mut Text>) { + let mut text = query.single_mut(); + text.sections[2].value = String::from("B"); + info!("B: One shot system registered with World was triggered"); +} + +fn setup_ui(mut commands: Commands) { + commands.spawn(Camera2dBundle::default()); + commands.spawn( + TextBundle::from_sections([ + TextSection::new( + "Press A or B to trigger a one-shot system\n", + TextStyle { + font_size: 25.0, + ..default() + }, + ), + TextSection::new( + "Last Triggered: ", + TextStyle { + font_size: 20.0, + ..default() + }, + ), + TextSection::new( + "-", + TextStyle { + font_size: 20.0, + color: bevy::color::palettes::css::ORANGE.into(), + ..default() + }, + ), + ]) + .with_text_justify(JustifyText::Center) + .with_style(Style { + align_self: AlignSelf::Center, + justify_self: JustifySelf::Center, + ..default() + }), + ); +}