use bevy::{
ecs::system::{RunSystemOnce, SystemId},
prelude::*,
};
fn main() {
App::new()
.add_plugins(DefaultPlugins)
.add_systems(
Startup,
(
setup_ui,
setup_with_commands,
setup_with_world.after(setup_ui), ),
)
.add_systems(Update, (trigger_system, evaluate_callbacks).chain())
.run();
}
#[derive(Component)]
struct Callback(SystemId);
#[derive(Component)]
struct Triggered;
#[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 setup_with_world(world: &mut World) {
world.run_system_once(system_b);
let system_id = world.register_system(system_b);
world.spawn((Callback(system_id), B));
}
fn trigger_system(
mut commands: Commands,
query_a: Query<Entity, With<A>>,
query_b: Query<Entity, With<B>>,
input: Res<ButtonInput<KeyCode>>,
) {
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);
}
}
fn evaluate_callbacks(query: Query<(Entity, &Callback), With<Triggered>>, mut commands: Commands) {
for (entity, callback) in query.iter() {
commands.run_system(callback.0);
commands.entity(entity).remove::<Triggered>();
}
}
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()
}),
);
}