mirror of
https://github.com/bevyengine/bevy
synced 2024-11-30 00:20:20 +00:00
7482a0d26d
Fixes #15834 ## Migration Guide The APIs of `Time`, `Timer` and `Stopwatch` have been cleaned up for consistency with each other and the standard library's `Duration` type. The following methods have been renamed: - `Stowatch::paused` -> `Stopwatch::is_paused` - `Time::elapsed_seconds` -> `Time::elasped_secs` (including `_f64` and `_wrapped` variants)
57 lines
2.2 KiB
Rust
57 lines
2.2 KiB
Rust
//! This example shows how you can know when a [`Component`] has been removed, so you can react to it.
|
|
//!
|
|
//! When a [`Component`] is removed from an [`Entity`], all [`Observer`] with an [`OnRemove`] trigger for
|
|
//! that [`Component`] will be notified. These observers will be called immediately after the
|
|
//! [`Component`] is removed. For more info on observers, see the
|
|
//! [observers example](https://github.com/bevyengine/bevy/blob/main/examples/ecs/observers.rs).
|
|
//!
|
|
//! Advanced users may also consider using a lifecycle hook
|
|
//! instead of an observer, as it incurs less overhead for a case like this.
|
|
//! See the [component hooks example](https://github.com/bevyengine/bevy/blob/main/examples/ecs/component_hooks.rs).
|
|
use bevy::prelude::*;
|
|
|
|
fn main() {
|
|
App::new()
|
|
.add_plugins(DefaultPlugins)
|
|
.add_systems(Startup, setup)
|
|
// This system will remove a component after two seconds.
|
|
.add_systems(Update, remove_component)
|
|
// This observer will react to the removal of the component.
|
|
.add_observer(react_on_removal)
|
|
.run();
|
|
}
|
|
|
|
/// This `struct` is just used for convenience in this example. This is the [`Component`] we'll be
|
|
/// giving to the `Entity` so we have a [`Component`] to remove in `remove_component()`.
|
|
#[derive(Component)]
|
|
struct MyComponent;
|
|
|
|
fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
|
|
commands.spawn(Camera2d);
|
|
commands.spawn((
|
|
Sprite::from_image(asset_server.load("branding/icon.png")),
|
|
// Add the `Component`.
|
|
MyComponent,
|
|
));
|
|
}
|
|
|
|
fn remove_component(
|
|
time: Res<Time>,
|
|
mut commands: Commands,
|
|
query: Query<Entity, With<MyComponent>>,
|
|
) {
|
|
// After two seconds have passed the `Component` is removed.
|
|
if time.elapsed_secs() > 2.0 {
|
|
if let Some(entity) = query.iter().next() {
|
|
commands.entity(entity).remove::<MyComponent>();
|
|
}
|
|
}
|
|
}
|
|
|
|
fn react_on_removal(trigger: Trigger<OnRemove, MyComponent>, mut query: Query<&mut Sprite>) {
|
|
// The `OnRemove` trigger was automatically called on the `Entity` that had its `MyComponent` removed.
|
|
let entity = trigger.entity();
|
|
if let Ok(mut sprite) = query.get_mut(entity) {
|
|
sprite.color = Color::srgb(0.5, 1., 1.);
|
|
}
|
|
}
|