b6a647cc01
Adds a `default()` shorthand for `Default::default()` ... because life is too short to constantly type `Default::default()`.
```rust
use bevy::prelude::*;
#[derive(Default)]
struct Foo {
bar: usize,
baz: usize,
}
// Normally you would do this:
let foo = Foo {
bar: 10,
..Default::default()
};
// But now you can do this:
let foo = Foo {
bar: 10,
..default()
};
```
The examples have been adapted to use `..default()`. I've left internal crates as-is for now because they don't pull in the bevy prelude, and the ergonomics of each case should be considered individually.
61 lines
2.3 KiB
Rust
61 lines
2.3 KiB
Rust
// This example shows how you can know when a `Component` has been removed, so you can react to it.
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use bevy::prelude::*;
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fn main() {
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// Information regarding removed `Component`s is discarded at the end of each frame, so you need
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// to react to the removal before the frame is over.
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//
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// Also, `Components` are removed via a `Command`. `Command`s are applied after a stage has
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// finished executing. So you need to react to the removal at some stage after the
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// `Component` is removed.
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//
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// With these constraints in mind we make sure to place the system that removes a `Component` on
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// the `CoreStage::Update' stage, and the system that reacts on the removal on the
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// `CoreStage::PostUpdate` stage.
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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_to_stage(CoreStage::Update, remove_component)
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.add_system_to_stage(CoreStage::PostUpdate, react_on_removal)
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.run();
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}
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// This `Struct` is just used for convenience in this example. This is the `Component` we'll be
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// giving to the `Entity` so we have a `Component` to remove in `remove_component()`.
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#[derive(Component)]
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struct MyComponent;
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fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
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commands.spawn_bundle(OrthographicCameraBundle::new_2d());
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commands
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.spawn_bundle(SpriteBundle {
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texture: asset_server.load("branding/icon.png"),
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..default()
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})
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.insert(MyComponent); // Add the `Component`.
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}
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fn remove_component(
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time: Res<Time>,
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mut commands: Commands,
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query: Query<Entity, With<MyComponent>>,
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) {
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// After two seconds have passed the `Component` is removed.
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if time.seconds_since_startup() > 2.0 {
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if let Some(entity) = query.iter().next() {
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commands.entity(entity).remove::<MyComponent>();
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}
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}
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}
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fn react_on_removal(removed: RemovedComponents<MyComponent>, mut query: Query<&mut Sprite>) {
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// `RemovedComponents<T>::iter()` returns an interator with the `Entity`s that had their
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// `Component` `T` (in this case `MyComponent`) removed at some point earlier during the frame.
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for entity in removed.iter() {
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if let Ok(mut sprite) = query.get_mut(entity) {
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sprite.color.set_r(0.0);
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}
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}
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}
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