57c021538e
# Objective Noticed a warning when running tests: ``` > cargo test --workspace warning: output filename collision. The example target `change_detection` in package `bevy_ecs v0.5.0 (/bevy/crates/bevy_ecs)` has the same output filename as the example target `change_detection` in package `bevy v0.5.0 (/bevy)`. Colliding filename is: /bevy/target/debug/examples/change_detection The targets should have unique names. Consider changing their names to be unique or compiling them separately. This may become a hard error in the future; see <https://github.com/rust-lang/cargo/issues/6313>. warning: output filename collision. The example target `change_detection` in package `bevy_ecs v0.5.0 (/bevy/crates/bevy_ecs)` has the same output filename as the example target `change_detection` in package `bevy v0.5.0 (/bevy)`. Colliding filename is: /bevy/target/debug/examples/change_detection.dSYM The targets should have unique names. Consider changing their names to be unique or compiling them separately. This may become a hard error in the future; see <https://github.com/rust-lang/cargo/issues/6313>. ``` ## Solution I renamed example `change_detection` to `component_change_detection`
52 lines
1.5 KiB
Rust
52 lines
1.5 KiB
Rust
use bevy::prelude::*;
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use rand::Rng;
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// This example illustrates how to react to component change
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fn main() {
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App::build()
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.add_plugins(DefaultPlugins)
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.add_startup_system(setup.system())
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.add_system(change_component.system())
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.add_system(change_detection.system())
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.add_system(tracker_monitoring.system())
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.run();
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}
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#[derive(Debug)]
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struct MyComponent(f64);
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fn setup(mut commands: Commands) {
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commands.spawn().insert(MyComponent(0.));
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commands.spawn().insert(Transform::identity());
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}
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fn change_component(time: Res<Time>, mut query: Query<(Entity, &mut MyComponent)>) {
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for (entity, mut component) in query.iter_mut() {
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if rand::thread_rng().gen_bool(0.1) {
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info!("changing component {:?}", entity);
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component.0 = time.seconds_since_startup();
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}
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}
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}
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// There are query filters for `Changed<T>` and `Added<T>`
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// Only entities matching the filters will be in the query
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fn change_detection(query: Query<(Entity, &MyComponent), Changed<MyComponent>>) {
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for (entity, component) in query.iter() {
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info!("{:?} changed: {:?}", entity, component,);
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}
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}
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// By looking at trackers, the query is not filtered but the information is available
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fn tracker_monitoring(
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query: Query<(
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Entity,
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Option<&MyComponent>,
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Option<ChangeTrackers<MyComponent>>,
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)>,
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) {
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for (entity, component, trackers) in query.iter() {
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info!("{:?}: {:?} -> {:?}", entity, component, trackers);
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}
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}
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