b724a0f586
# Objective - Remove all the `.system()` possible. - Check for remaining missing cases. ## Solution - Remove all `.system()`, fix compile errors - 32 calls to `.system()` remains, mostly internals, the few others should be removed after #2446
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::new()
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.add_plugins(DefaultPlugins)
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.add_startup_system(setup)
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.add_system(change_component)
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.add_system(change_detection)
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.add_system(tracker_monitoring)
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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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