use bevy::prelude::*;
use rand::Rng;
fn main() {
App::new()
.add_plugins(DefaultPlugins)
.add_systems(Startup, setup)
.add_systems(
Update,
(change_component, change_detection, tracker_monitoring),
)
.run();
}
#[derive(Component, PartialEq, Debug)]
struct MyComponent(f32);
fn setup(mut commands: Commands) {
commands.spawn(MyComponent(0.));
commands.spawn(Transform::IDENTITY);
}
fn change_component(time: Res<Time>, mut query: Query<(Entity, &mut MyComponent)>) {
for (entity, mut component) in &mut query {
if rand::thread_rng().gen_bool(0.1) {
info!("changing component {:?}", entity);
let new_component = MyComponent(time.elapsed_seconds().round());
component.set_if_neq(new_component);
}
}
}
fn change_detection(query: Query<(Entity, &MyComponent), Changed<MyComponent>>) {
for (entity, component) in &query {
info!("{:?} changed: {:?}", entity, component);
}
}
fn tracker_monitoring(query: Query<(Entity, Ref<MyComponent>)>) {
for (entity, component) in &query {
info!(
"{:?}: {:?} -> {{is_added: {}, is_changed: {}}}",
entity,
component,
component.is_added(),
component.is_changed()
);
}
}