bevy/examples/ecs/component_change_detection.rs
Carter Anderson 11b41206eb Add upstream bevy_ecs and prepare for custom-shaders merge (#2815)
This updates the `pipelined-rendering` branch to use the latest `bevy_ecs` from `main`. This accomplishes a couple of goals:

1. prepares for upcoming `custom-shaders` branch changes, which were what drove many of the recent bevy_ecs changes on `main`
2. prepares for the soon-to-happen merge of `pipelined-rendering` into `main`. By including bevy_ecs changes now, we make that merge simpler / easier to review. 

I split this up into 3 commits:

1. **add upstream bevy_ecs**: please don't bother reviewing this content. it has already received thorough review on `main` and is a literal copy/paste of the relevant folders (the old folders were deleted so the directories are literally exactly the same as `main`).
2. **support manual buffer application in stages**: this is used to enable the Extract step. we've already reviewed this once on the `pipelined-rendering` branch, but its worth looking at one more time in the new context of (1).
3. **support manual archetype updates in QueryState**: same situation as (2).
2021-09-14 06:14:19 +00:00

51 lines
1.5 KiB
Rust

use bevy::prelude::*;
use rand::Rng;
// This example illustrates how to react to component change
fn main() {
App::new()
.add_plugins(DefaultPlugins)
.add_startup_system(setup)
.add_system(change_component)
.add_system(change_detection)
.add_system(tracker_monitoring)
.run();
}
#[derive(Debug)]
struct MyComponent(f64);
fn setup(mut commands: Commands) {
commands.spawn().insert(MyComponent(0.));
commands.spawn().insert(Transform::identity());
}
fn change_component(time: Res<Time>, mut query: Query<(Entity, &mut MyComponent)>) {
for (entity, mut component) in query.iter_mut() {
if rand::thread_rng().gen_bool(0.1) {
info!("changing component {:?}", entity);
component.0 = time.seconds_since_startup();
}
}
}
// There are query filters for `Changed<T>` and `Added<T>`
// Only entities matching the filters will be in the query
fn change_detection(query: Query<(Entity, &MyComponent), Changed<MyComponent>>) {
for (entity, component) in query.iter() {
info!("{:?} changed: {:?}", entity, component,);
}
}
// By looking at trackers, the query is not filtered but the information is available
fn tracker_monitoring(
query: Query<(
Entity,
Option<&MyComponent>,
Option<ChangeTrackers<MyComponent>>,
)>,
) {
for (entity, component, trackers) in query.iter() {
info!("{:?}: {:?} -> {:?}", entity, component, trackers);
}
}