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Remove entity placeholder from observers (#19440)

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# Objective

`Entity::PLACEHOLDER` acts as a magic number that will *probably* never
really exist, but it certainly could. And, `Entity` has a niche, so the
only reason to use `PLACEHOLDER` is as an alternative to `MaybeUninit`
that trades safety risks for logic risks.

As a result, bevy has generally advised against using `PLACEHOLDER`, but
we still use if for a lot internally. This pr starts removing internal
uses of it, starting from observers.

## Solution

Change all trigger target related types from `Entity` to
`Option<Entity>`

Small migration guide to come.

## Testing

CI

## Future Work

This turned a lot of code from 

```rust
trigger.target()
```

to 

```rust
trigger.target().unwrap()
```

The extra panic is no worse than before; it's just earlier than
panicking after passing the placeholder to something else.

But this is kinda annoying. 

I would like to add a `TriggerMode` or something to `Event` that would
restrict what kinds of targets can be used for that event. Many events
like `Removed` etc, are always triggered with a target. We can make
those have a way to assume Some, etc. But I wanted to save that for a
future pr.
This commit is contained in:
Eagster 2025-06-09 15:37:56 -04:00 committed by GitHub
parent 860ff7819b
commit 064e5e48b4
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
30 changed files with 134 additions and 99 deletions
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4
crates/bevy_ecs/README.md
View File

@ -340,8 +340,8 @@ let mut world = World::new();
let entity = world.spawn_empty().id();
world.add_observer(|trigger: Trigger<Explode>, mut commands: Commands| {
println!("Entity {} goes BOOM!", trigger.target());
commands.entity(trigger.target()).despawn();
println!("Entity {} goes BOOM!", trigger.target().unwrap());
commands.entity(trigger.target().unwrap()).despawn();
});
world.flush();

16
crates/bevy_ecs/src/bundle.rs
View File

@ -1143,7 +1143,7 @@ impl<'w> BundleInserter<'w> {
if archetype.has_replace_observer() {
deferred_world.trigger_observers(
ON_REPLACE,
entity,
Some(entity),
archetype_after_insert.iter_existing(),
caller,
);
@ -1328,7 +1328,7 @@ impl<'w> BundleInserter<'w> {
if new_archetype.has_add_observer() {
deferred_world.trigger_observers(
ON_ADD,
entity,
Some(entity),
archetype_after_insert.iter_added(),
caller,
);
@ -1346,7 +1346,7 @@ impl<'w> BundleInserter<'w> {
if new_archetype.has_insert_observer() {
deferred_world.trigger_observers(
ON_INSERT,
entity,
Some(entity),
archetype_after_insert.iter_inserted(),
caller,
);
@ -1365,7 +1365,7 @@ impl<'w> BundleInserter<'w> {
if new_archetype.has_insert_observer() {
deferred_world.trigger_observers(
ON_INSERT,
entity,
Some(entity),
archetype_after_insert.iter_added(),
caller,
);
@ -1519,7 +1519,7 @@ impl<'w> BundleRemover<'w> {
if self.old_archetype.as_ref().has_replace_observer() {
deferred_world.trigger_observers(
ON_REPLACE,
entity,
Some(entity),
bundle_components_in_archetype(),
caller,
);
@ -1534,7 +1534,7 @@ impl<'w> BundleRemover<'w> {
if self.old_archetype.as_ref().has_remove_observer() {
deferred_world.trigger_observers(
ON_REMOVE,
entity,
Some(entity),
bundle_components_in_archetype(),
caller,
);
@ -1785,7 +1785,7 @@ impl<'w> BundleSpawner<'w> {
if archetype.has_add_observer() {
deferred_world.trigger_observers(
ON_ADD,
entity,
Some(entity),
bundle_info.iter_contributed_components(),
caller,
);
@ -1800,7 +1800,7 @@ impl<'w> BundleSpawner<'w> {
if archetype.has_insert_observer() {
deferred_world.trigger_observers(
ON_INSERT,
entity,
Some(entity),
bundle_info.iter_contributed_components(),
caller,
);

34
crates/bevy_ecs/src/observer/mod.rs
View File

@ -68,7 +68,7 @@ impl<'w, E, B: Bundle> Trigger<'w, E, B> {
}
/// Returns the [`Entity`] that was targeted by the `event` that triggered this observer. It may
/// be [`Entity::PLACEHOLDER`].
/// be [`None`] if the trigger is not for a particular entity.
///
/// Observable events can target specific entities. When those events fire, they will trigger
/// any observers on the targeted entities. In this case, the `target()` and `observer()` are
@ -81,7 +81,7 @@ impl<'w, E, B: Bundle> Trigger<'w, E, B> {
///
/// This is an important distinction: the entity reacting to an event is not always the same as
/// the entity triggered by the event.
pub fn target(&self) -> Entity {
pub fn target(&self) -> Option<Entity> {
self.trigger.target
}
@ -341,7 +341,7 @@ pub struct ObserverTrigger {
/// The [`ComponentId`]s the trigger targeted.
components: SmallVec<[ComponentId; 2]>,
/// The entity the trigger targeted.
pub target: Entity,
pub target: Option<Entity>,
/// The location of the source code that triggered the observer.
pub caller: MaybeLocation,
}
@ -416,7 +416,7 @@ impl Observers {
pub(crate) fn invoke<T>(
mut world: DeferredWorld,
event_type: ComponentId,
target: Entity,
target: Option<Entity>,
components: impl Iterator<Item = ComponentId> + Clone,
data: &mut T,
propagate: &mut bool,
@ -455,8 +455,8 @@ impl Observers {
observers.map.iter().for_each(&mut trigger_observer);
// Trigger entity observers listening for this kind of trigger
if target != Entity::PLACEHOLDER {
if let Some(map) = observers.entity_observers.get(&target) {
if let Some(target_entity) = target {
if let Some(map) = observers.entity_observers.get(&target_entity) {
map.iter().for_each(&mut trigger_observer);
}
}
@ -469,8 +469,8 @@ impl Observers {
.iter()
.for_each(&mut trigger_observer);
if target != Entity::PLACEHOLDER {
if let Some(map) = component_observers.entity_map.get(&target) {
if let Some(target_entity) = target {
if let Some(map) = component_observers.entity_map.get(&target_entity) {
map.iter().for_each(&mut trigger_observer);
}
}
@ -695,7 +695,7 @@ impl World {
unsafe {
world.trigger_observers_with_data::<_, E::Traversal>(
event_id,
Entity::PLACEHOLDER,
None,
targets.components(),
event_data,
false,
@ -708,7 +708,7 @@ impl World {
unsafe {
world.trigger_observers_with_data::<_, E::Traversal>(
event_id,
target_entity,
Some(target_entity),
targets.components(),
event_data,
E::AUTO_PROPAGATE,
@ -999,20 +999,20 @@ mod tests {
world.add_observer(
|obs: Trigger<OnAdd, A>, mut res: ResMut<Order>, mut commands: Commands| {
res.observed("add_a");
commands.entity(obs.target()).insert(B);
commands.entity(obs.target().unwrap()).insert(B);
},
);
world.add_observer(
|obs: Trigger<OnRemove, A>, mut res: ResMut<Order>, mut commands: Commands| {
res.observed("remove_a");
commands.entity(obs.target()).remove::<B>();
commands.entity(obs.target().unwrap()).remove::<B>();
},
);
world.add_observer(
|obs: Trigger<OnAdd, B>, mut res: ResMut<Order>, mut commands: Commands| {
res.observed("add_b");
commands.entity(obs.target()).remove::<A>();
commands.entity(obs.target().unwrap()).remove::<A>();
},
);
world.add_observer(|_: Trigger<OnRemove, B>, mut res: ResMut<Order>| {
@ -1181,7 +1181,7 @@ mod tests {
};
world.spawn_empty().observe(system);
world.add_observer(move |obs: Trigger<EventA>, mut res: ResMut<Order>| {
assert_eq!(obs.target(), Entity::PLACEHOLDER);
assert_eq!(obs.target(), None);
res.observed("event_a");
});
@ -1208,7 +1208,7 @@ mod tests {
.observe(|_: Trigger<EventA>, mut res: ResMut<Order>| res.observed("a_1"))
.id();
world.add_observer(move |obs: Trigger<EventA>, mut res: ResMut<Order>| {
assert_eq!(obs.target(), entity);
assert_eq!(obs.target().unwrap(), entity);
res.observed("a_2");
});
@ -1628,7 +1628,7 @@ mod tests {
world.add_observer(
|trigger: Trigger<EventPropagating>, query: Query<&A>, mut res: ResMut<Order>| {
if query.get(trigger.target()).is_ok() {
if query.get(trigger.target().unwrap()).is_ok() {
res.observed("event");
}
},
@ -1651,7 +1651,7 @@ mod tests {
fn observer_modifies_relationship() {
fn on_add(trigger: Trigger<OnAdd, A>, mut commands: Commands) {
commands
.entity(trigger.target())
.entity(trigger.target().unwrap())
.with_related_entities::<crate::hierarchy::ChildOf>(|rsc| {
rsc.spawn_empty();
});

6
crates/bevy_ecs/src/observer/runner.rs
View File

@ -123,8 +123,8 @@ pub type ObserverRunner = fn(DeferredWorld, ObserverTrigger, PtrMut, propagate:
/// struct Explode;
///
/// world.add_observer(|trigger: Trigger<Explode>, mut commands: Commands| {
/// println!("Entity {} goes BOOM!", trigger.target());
/// commands.entity(trigger.target()).despawn();
/// println!("Entity {} goes BOOM!", trigger.target().unwrap());
/// commands.entity(trigger.target().unwrap()).despawn();
/// });
///
/// world.flush();
@ -157,7 +157,7 @@ pub type ObserverRunner = fn(DeferredWorld, ObserverTrigger, PtrMut, propagate:
/// # struct Explode;
/// world.entity_mut(e1).observe(|trigger: Trigger<Explode>, mut commands: Commands| {
/// println!("Boom!");
/// commands.entity(trigger.target()).despawn();
/// commands.entity(trigger.target().unwrap()).despawn();
/// });
///
/// world.entity_mut(e2).observe(|trigger: Trigger<Explode>, mut commands: Commands| {

41
crates/bevy_ecs/src/world/deferred_world.rs
View File

@ -23,7 +23,7 @@ use super::{unsafe_world_cell::UnsafeWorldCell, Mut, World, ON_INSERT, ON_REPLAC
///
/// This means that in order to add entities, for example, you will need to use commands instead of the world directly.
pub struct DeferredWorld<'w> {
// SAFETY: Implementors must not use this reference to make structural changes
// SAFETY: Implementers must not use this reference to make structural changes
world: UnsafeWorldCell<'w>,
}
@ -157,7 +157,7 @@ impl<'w> DeferredWorld<'w> {
if archetype.has_replace_observer() {
self.trigger_observers(
ON_REPLACE,
entity,
Some(entity),
[component_id].into_iter(),
MaybeLocation::caller(),
);
@ -197,7 +197,7 @@ impl<'w> DeferredWorld<'w> {
if archetype.has_insert_observer() {
self.trigger_observers(
ON_INSERT,
entity,
Some(entity),
[component_id].into_iter(),
MaybeLocation::caller(),
);
@ -738,7 +738,7 @@ impl<'w> DeferredWorld<'w> {
pub(crate) unsafe fn trigger_observers(
&mut self,
event: ComponentId,
target: Entity,
target: Option<Entity>,
components: impl Iterator<Item = ComponentId> + Clone,
caller: MaybeLocation,
) {
@ -761,7 +761,7 @@ impl<'w> DeferredWorld<'w> {
pub(crate) unsafe fn trigger_observers_with_data<E, T>(
&mut self,
event: ComponentId,
mut target: Entity,
target: Option<Entity>,
components: impl Iterator<Item = ComponentId> + Clone,
data: &mut E,
mut propagate: bool,
@ -769,18 +769,20 @@ impl<'w> DeferredWorld<'w> {
) where
T: Traversal<E>,
{
Observers::invoke::<_>(
self.reborrow(),
event,
target,
components.clone(),
data,
&mut propagate,
caller,
);
let Some(mut target) = target else { return };
loop {
Observers::invoke::<_>(
self.reborrow(),
event,
target,
components.clone(),
data,
&mut propagate,
caller,
);
if !propagate {
break;
return;
}
if let Some(traverse_to) = self
.get_entity(target)
@ -792,6 +794,15 @@ impl<'w> DeferredWorld<'w> {
} else {
break;
}
Observers::invoke::<_>(
self.reborrow(),
event,
Some(target),
components.clone(),
data,
&mut propagate,
caller,
);
}
}

12
crates/bevy_ecs/src/world/entity_ref.rs
View File

@ -2371,7 +2371,7 @@ impl<'w> EntityWorldMut<'w> {
if archetype.has_despawn_observer() {
deferred_world.trigger_observers(
ON_DESPAWN,
self.entity,
Some(self.entity),
archetype.components(),
caller,
);
@ -2385,7 +2385,7 @@ impl<'w> EntityWorldMut<'w> {
if archetype.has_replace_observer() {
deferred_world.trigger_observers(
ON_REPLACE,
self.entity,
Some(self.entity),
archetype.components(),
caller,
);
@ -2400,7 +2400,7 @@ impl<'w> EntityWorldMut<'w> {
if archetype.has_remove_observer() {
deferred_world.trigger_observers(
ON_REMOVE,
self.entity,
Some(self.entity),
archetype.components(),
caller,
);
@ -5749,7 +5749,9 @@ mod tests {
let entity = world
.spawn_empty()
.observe(|trigger: Trigger<TestEvent>, mut commands: Commands| {
commands.entity(trigger.target()).insert(TestComponent(0));
commands
.entity(trigger.target().unwrap())
.insert(TestComponent(0));
})
.id();
@ -5769,7 +5771,7 @@ mod tests {
let mut world = World::new();
world.add_observer(
|trigger: Trigger<OnAdd, TestComponent>, mut commands: Commands| {
commands.entity(trigger.target()).despawn();
commands.entity(trigger.target().unwrap()).despawn();
},
);
let entity = world.spawn_empty().id();

2
crates/bevy_input_focus/src/lib.rs
View File

@ -394,7 +394,7 @@ mod tests {
trigger: Trigger<FocusedInput<KeyboardInput>>,
mut query: Query<&mut GatherKeyboardEvents>,
) {
if let Ok(mut gather) = query.get_mut(trigger.target()) {
if let Ok(mut gather) = query.get_mut(trigger.target().unwrap()) {
if let Key::Character(c) = &trigger.input.logical_key {
gather.0.push_str(c.as_str());
}

6
crates/bevy_pbr/src/render/light.rs
View File

@ -551,7 +551,7 @@ pub(crate) fn add_light_view_entities(
trigger: Trigger<OnAdd, (ExtractedDirectionalLight, ExtractedPointLight)>,
mut commands: Commands,
) {
if let Ok(mut v) = commands.get_entity(trigger.target()) {
if let Ok(mut v) = commands.get_entity(trigger.target().unwrap()) {
v.insert(LightViewEntities::default());
}
}
@ -561,7 +561,7 @@ pub(crate) fn extracted_light_removed(
trigger: Trigger<OnRemove, (ExtractedDirectionalLight, ExtractedPointLight)>,
mut commands: Commands,
) {
if let Ok(mut v) = commands.get_entity(trigger.target()) {
if let Ok(mut v) = commands.get_entity(trigger.target().unwrap()) {
v.try_remove::<LightViewEntities>();
}
}
@ -571,7 +571,7 @@ pub(crate) fn remove_light_view_entities(
query: Query<&LightViewEntities>,
mut commands: Commands,
) {
if let Ok(entities) = query.get(trigger.target()) {
if let Ok(entities) = query.get(trigger.target().unwrap()) {
for v in entities.0.values() {
for e in v.iter().copied() {
if let Ok(mut v) = commands.get_entity(e) {

6
crates/bevy_picking/src/lib.rs
View File

@ -55,13 +55,13 @@
//! // Spawn your entity here, e.g. a Mesh.
//! // When dragged, mutate the `Transform` component on the dragged target entity:
//! .observe(|trigger: Trigger<Pointer<Drag>>, mut transforms: Query<&mut Transform>| {
//! let mut transform = transforms.get_mut(trigger.target()).unwrap();
//! let mut transform = transforms.get_mut(trigger.target().unwrap()).unwrap();
//! let drag = trigger.event();
//! transform.rotate_local_y(drag.delta.x / 50.0);
//! })
//! .observe(|trigger: Trigger<Pointer<Click>>, mut commands: Commands| {
//! println!("Entity {} goes BOOM!", trigger.target());
//! commands.entity(trigger.target()).despawn();
//! println!("Entity {} goes BOOM!", trigger.target().unwrap());
//! commands.entity(trigger.target().unwrap()).despawn();
//! })
//! .observe(|trigger: Trigger<Pointer<Over>>, mut events: EventWriter<Greeting>| {
//! events.write(Greeting);

8
crates/bevy_render/src/sync_world.rs
View File

@ -94,14 +94,14 @@ impl Plugin for SyncWorldPlugin {
app.init_resource::<PendingSyncEntity>();
app.add_observer(
|trigger: Trigger<OnAdd, SyncToRenderWorld>, mut pending: ResMut<PendingSyncEntity>| {
pending.push(EntityRecord::Added(trigger.target()));
pending.push(EntityRecord::Added(trigger.target().unwrap()));
},
);
app.add_observer(
|trigger: Trigger<OnRemove, SyncToRenderWorld>,
mut pending: ResMut<PendingSyncEntity>,
query: Query<&RenderEntity>| {
if let Ok(e) = query.get(trigger.target()) {
if let Ok(e) = query.get(trigger.target().unwrap()) {
pending.push(EntityRecord::Removed(*e));
};
},
@ -512,14 +512,14 @@ mod tests {
main_world.add_observer(
|trigger: Trigger<OnAdd, SyncToRenderWorld>, mut pending: ResMut<PendingSyncEntity>| {
pending.push(EntityRecord::Added(trigger.target()));
pending.push(EntityRecord::Added(trigger.target().unwrap()));
},
);
main_world.add_observer(
|trigger: Trigger<OnRemove, SyncToRenderWorld>,
mut pending: ResMut<PendingSyncEntity>,
query: Query<&RenderEntity>| {
if let Ok(e) = query.get(trigger.target()) {
if let Ok(e) = query.get(trigger.target().unwrap()) {
pending.push(EntityRecord::Removed(*e));
};
},

10
crates/bevy_scene/src/scene_spawner.rs
View File

@ -721,7 +721,7 @@ mod tests {
.expect("Failed to run dynamic scene builder system.")
}
fn observe_trigger(app: &mut App, scene_id: InstanceId, scene_entity: Entity) {
fn observe_trigger(app: &mut App, scene_id: InstanceId, scene_entity: Option<Entity>) {
// Add observer
app.world_mut().add_observer(
move |trigger: Trigger<SceneInstanceReady>,
@ -773,7 +773,7 @@ mod tests {
.unwrap();
// Check trigger.
observe_trigger(&mut app, scene_id, Entity::PLACEHOLDER);
observe_trigger(&mut app, scene_id, None);
}
#[test]
@ -792,7 +792,7 @@ mod tests {
.unwrap();
// Check trigger.
observe_trigger(&mut app, scene_id, Entity::PLACEHOLDER);
observe_trigger(&mut app, scene_id, None);
}
#[test]
@ -816,7 +816,7 @@ mod tests {
.unwrap();
// Check trigger.
observe_trigger(&mut app, scene_id, scene_entity);
observe_trigger(&mut app, scene_id, Some(scene_entity));
}
#[test]
@ -840,7 +840,7 @@ mod tests {
.unwrap();
// Check trigger.
observe_trigger(&mut app, scene_id, scene_entity);
observe_trigger(&mut app, scene_id, Some(scene_entity));
}
#[test]

2
crates/bevy_winit/src/cursor.rs
View File

@ -194,7 +194,7 @@ fn update_cursors(
fn on_remove_cursor_icon(trigger: Trigger<OnRemove, CursorIcon>, mut commands: Commands) {
// Use `try_insert` to avoid panic if the window is being destroyed.
commands
.entity(trigger.target())
.entity(trigger.target().unwrap())
.try_insert(PendingCursor(Some(CursorSource::System(
convert_system_cursor_icon(SystemCursorIcon::Default),
))));

4
examples/3d/edit_material_on_gltf.rs
View File

@ -65,12 +65,12 @@ fn change_material(
mut asset_materials: ResMut<Assets<StandardMaterial>>,
) {
// Get the `ColorOverride` of the entity, if it does not have a color override, skip
let Ok(color_override) = color_override.get(trigger.target()) else {
let Ok(color_override) = color_override.get(trigger.target().unwrap()) else {
return;
};
// Iterate over all children recursively
for descendants in children.iter_descendants(trigger.target()) {
for descendants in children.iter_descendants(trigger.target().unwrap()) {
// Get the material of the descendant
if let Some(material) = mesh_materials
.get(descendants)

4
examples/animation/animated_mesh.rs
View File

@ -70,12 +70,12 @@ fn play_animation_when_ready(
) {
// The entity we spawned in `setup_mesh_and_animation` is the trigger's target.
// Start by finding the AnimationToPlay component we added to that entity.
if let Ok(animation_to_play) = animations_to_play.get(trigger.target()) {
if let Ok(animation_to_play) = animations_to_play.get(trigger.target().unwrap()) {
// The SceneRoot component will have spawned the scene as a hierarchy
// of entities parented to our entity. Since the asset contained a skinned
// mesh and animations, it will also have spawned an animation player
// component. Search our entity's descendants to find the animation player.
for child in children.iter_descendants(trigger.target()) {
for child in children.iter_descendants(trigger.target().unwrap()) {
if let Ok(mut player) = players.get_mut(child) {
// Tell the animation player to start the animation and keep
// repeating it.

5
examples/animation/animated_mesh_events.rs
View File

@ -47,7 +47,10 @@ fn observe_on_step(
transforms: Query<&GlobalTransform>,
mut seeded_rng: ResMut<SeededRng>,
) {
let translation = transforms.get(trigger.target()).unwrap().translation();
let translation = transforms
.get(trigger.target().unwrap())
.unwrap()
.translation();
// Spawn a bunch of particles.
for _ in 0..14 {
let horizontal = seeded_rng.0.r#gen::<Dir2>() * seeded_rng.0.gen_range(8.0..12.0);

2
examples/ecs/entity_disabling.rs
View File

@ -40,7 +40,7 @@ fn disable_entities_on_click(
valid_query: Query<&DisableOnClick>,
mut commands: Commands,
) {
let clicked_entity = trigger.target();
let clicked_entity = trigger.target().unwrap();
// Windows and text are entities and can be clicked!
// We definitely don't want to disable the window itself,
// because that would cause the app to close!

8
examples/ecs/observer_propagation.rs
View File

@ -78,14 +78,14 @@ fn attack_armor(entities: Query<Entity, With<Armor>>, mut commands: Commands) {
}
fn attack_hits(trigger: Trigger<Attack>, name: Query<&Name>) {
if let Ok(name) = name.get(trigger.target()) {
if let Ok(name) = name.get(trigger.target().unwrap()) {
info!("Attack hit {}", name);
}
}
/// A callback placed on [`Armor`], checking if it absorbed all the [`Attack`] damage.
fn block_attack(mut trigger: Trigger<Attack>, armor: Query<(&Armor, &Name)>) {
let (armor, name) = armor.get(trigger.target()).unwrap();
let (armor, name) = armor.get(trigger.target().unwrap()).unwrap();
let attack = trigger.event_mut();
let damage = attack.damage.saturating_sub(**armor);
if damage > 0 {
@ -110,14 +110,14 @@ fn take_damage(
mut app_exit: EventWriter<AppExit>,
) {
let attack = trigger.event();
let (mut hp, name) = hp.get_mut(trigger.target()).unwrap();
let (mut hp, name) = hp.get_mut(trigger.target().unwrap()).unwrap();
**hp = hp.saturating_sub(attack.damage);
if **hp > 0 {
info!("{} has {:.1} HP", name, hp.0);
} else {
warn!("💀 {} has died a gruesome death", name);
commands.entity(trigger.target()).despawn();
commands.entity(trigger.target().unwrap()).despawn();
app_exit.write(AppExit::Success);
}

14
examples/ecs/observers.rs
View File

@ -117,12 +117,16 @@ fn on_add_mine(
query: Query<&Mine>,
mut index: ResMut<SpatialIndex>,
) {
let mine = query.get(trigger.target()).unwrap();
let mine = query.get(trigger.target().unwrap()).unwrap();
let tile = (
(mine.pos.x / CELL_SIZE).floor() as i32,
(mine.pos.y / CELL_SIZE).floor() as i32,
);
index.map.entry(tile).or_default().insert(trigger.target());
index
.map
.entry(tile)
.or_default()
.insert(trigger.target().unwrap());
}
// Remove despawned mines from our index
@ -131,19 +135,19 @@ fn on_remove_mine(
query: Query<&Mine>,
mut index: ResMut<SpatialIndex>,
) {
let mine = query.get(trigger.target()).unwrap();
let mine = query.get(trigger.target().unwrap()).unwrap();
let tile = (
(mine.pos.x / CELL_SIZE).floor() as i32,
(mine.pos.y / CELL_SIZE).floor() as i32,
);
index.map.entry(tile).and_modify(|set| {
set.remove(&trigger.target());
set.remove(&trigger.target().unwrap());
});
}
fn explode_mine(trigger: Trigger<Explode>, query: Query<&Mine>, mut commands: Commands) {
// If a triggered event is targeting a specific entity you can access it with `.target()`
let id = trigger.target();
let id = trigger.target().unwrap();
let Ok(mut entity) = commands.get_entity(id) else {
return;
};

2
examples/ecs/removal_detection.rs
View File

@ -50,7 +50,7 @@ fn remove_component(
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.target();
let entity = trigger.target().unwrap();
if let Ok(mut sprite) = query.get_mut(entity) {
sprite.color = Color::srgb(0.5, 1., 1.);
}

5
examples/no_std/library/src/lib.rs
View File

@ -127,7 +127,10 @@ fn tick_timers(
}
fn unwrap<B: Bundle>(trigger: Trigger<Unwrap>, world: &mut World) {
if let Ok(mut target) = world.get_entity_mut(trigger.target()) {
if let Some(mut target) = trigger
.target()
.and_then(|target| world.get_entity_mut(target).ok())
{
if let Some(DelayedComponent(bundle)) = target.take::<DelayedComponent<B>>() {
target.insert(bundle);
}

6
examples/picking/debug_picking.rs
View File

@ -48,13 +48,13 @@ fn setup_scene(
.observe(on_click_spawn_cube)
.observe(
|out: Trigger<Pointer<Out>>, mut texts: Query<&mut TextColor>| {
let mut text_color = texts.get_mut(out.target()).unwrap();
let mut text_color = texts.get_mut(out.target().unwrap()).unwrap();
text_color.0 = Color::WHITE;
},
)
.observe(
|over: Trigger<Pointer<Over>>, mut texts: Query<&mut TextColor>| {
let mut color = texts.get_mut(over.target()).unwrap();
let mut color = texts.get_mut(over.target().unwrap()).unwrap();
color.0 = bevy::color::palettes::tailwind::CYAN_400.into();
},
);
@ -102,7 +102,7 @@ fn on_click_spawn_cube(
}
fn on_drag_rotate(drag: Trigger<Pointer<Drag>>, mut transforms: Query<&mut Transform>) {
if let Ok(mut transform) = transforms.get_mut(drag.target()) {
if let Ok(mut transform) = transforms.get_mut(drag.target().unwrap()) {
transform.rotate_y(drag.delta.x * 0.02);
transform.rotate_x(drag.delta.y * 0.02);
}

4
examples/picking/mesh_picking.rs
View File

@ -164,7 +164,7 @@ fn update_material_on<E>(
// versions of this observer, each triggered by a different event and with a different hardcoded
// material. Instead, the event type is a generic, and the material is passed in.
move |trigger, mut query| {
if let Ok(mut material) = query.get_mut(trigger.target()) {
if let Ok(mut material) = query.get_mut(trigger.target().unwrap()) {
material.0 = new_material.clone();
}
}
@ -191,7 +191,7 @@ fn rotate(mut query: Query<&mut Transform, With<Shape>>, time: Res<Time>) {
/// An observer to rotate an entity when it is dragged
fn rotate_on_drag(drag: Trigger<Pointer<Drag>>, mut transforms: Query<&mut Transform>) {
let mut transform = transforms.get_mut(drag.target()).unwrap();
let mut transform = transforms.get_mut(drag.target().unwrap()).unwrap();
transform.rotate_y(drag.delta.x * 0.02);
transform.rotate_x(drag.delta.y * 0.02);
}

6
examples/picking/simple_picking.rs
View File

@ -27,13 +27,13 @@ fn setup_scene(
.observe(on_click_spawn_cube)
.observe(
|out: Trigger<Pointer<Out>>, mut texts: Query<&mut TextColor>| {
let mut text_color = texts.get_mut(out.target()).unwrap();
let mut text_color = texts.get_mut(out.target().unwrap()).unwrap();
text_color.0 = Color::WHITE;
},
)
.observe(
|over: Trigger<Pointer<Over>>, mut texts: Query<&mut TextColor>| {
let mut color = texts.get_mut(over.target()).unwrap();
let mut color = texts.get_mut(over.target().unwrap()).unwrap();
color.0 = bevy::color::palettes::tailwind::CYAN_400.into();
},
);
@ -80,7 +80,7 @@ fn on_click_spawn_cube(
}
fn on_drag_rotate(drag: Trigger<Pointer<Drag>>, mut transforms: Query<&mut Transform>) {
if let Ok(mut transform) = transforms.get_mut(drag.target()) {
if let Ok(mut transform) = transforms.get_mut(drag.target().unwrap()) {
transform.rotate_y(drag.delta.x * 0.02);
transform.rotate_x(drag.delta.y * 0.02);
}

2
examples/picking/sprite_picking.rs
View File

@ -152,7 +152,7 @@ fn setup_atlas(
// An observer listener that changes the target entity's color.
fn recolor_on<E: Debug + Clone + Reflect>(color: Color) -> impl Fn(Trigger<E>, Query<&mut Sprite>) {
move |ev, mut sprites| {
let Ok(mut sprite) = sprites.get_mut(ev.target()) else {
let Ok(mut sprite) = sprites.get_mut(ev.target().unwrap()) else {
return;
};
sprite.color = color;

2
examples/testbed/3d.rs
View File

@ -281,7 +281,7 @@ mod animation {
animation: Res<Animation>,
mut players: Query<(Entity, &mut AnimationPlayer)>,
) {
for child in children.iter_descendants(trigger.target()) {
for child in children.iter_descendants(trigger.target().unwrap()) {
if let Ok((entity, mut player)) = players.get_mut(child) {
let mut transitions = AnimationTransitions::new();
transitions

2
examples/ui/directional_navigation.rs
View File

@ -70,7 +70,7 @@ fn universal_button_click_behavior(
mut trigger: Trigger<Pointer<Click>>,
mut button_query: Query<(&mut BackgroundColor, &mut ResetTimer)>,
) {
let button_entity = trigger.target();
let button_entity = trigger.target().unwrap();
if let Ok((mut color, mut reset_timer)) = button_query.get_mut(button_entity) {
// This would be a great place to play a little sound effect too!
color.0 = PRESSED_BUTTON.into();

2
examples/ui/scroll.rs
View File

@ -93,7 +93,7 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
mut commands: Commands
| {
if trigger.event().button == PointerButton::Primary {
commands.entity(trigger.target()).despawn();
commands.entity(trigger.target().unwrap()).despawn();
}
});
}

2
examples/ui/tab_navigation.rs
View File

@ -142,7 +142,7 @@ fn setup(mut commands: Commands) {
.observe(
|mut trigger: Trigger<Pointer<Click>>,
mut focus: ResMut<InputFocus>| {
focus.0 = Some(trigger.target());
focus.0 = Some(trigger.target().unwrap());
trigger.propagate(false);
},
);

4
examples/ui/viewport_node.rs
View File

@ -91,7 +91,7 @@ fn test(
fn on_drag_viewport(drag: Trigger<Pointer<Drag>>, mut node_query: Query<&mut Node>) {
if matches!(drag.button, PointerButton::Secondary) {
let mut node = node_query.get_mut(drag.target()).unwrap();
let mut node = node_query.get_mut(drag.target().unwrap()).unwrap();
if let (Val::Px(top), Val::Px(left)) = (node.top, node.left) {
node.left = Val::Px(left + drag.delta.x);
@ -102,7 +102,7 @@ fn on_drag_viewport(drag: Trigger<Pointer<Drag>>, mut node_query: Query<&mut Nod
fn on_drag_cuboid(drag: Trigger<Pointer<Drag>>, mut transform_query: Query<&mut Transform>) {
if matches!(drag.button, PointerButton::Primary) {
let mut transform = transform_query.get_mut(drag.target()).unwrap();
let mut transform = transform_query.get_mut(drag.target().unwrap()).unwrap();
transform.rotate_y(drag.delta.x * 0.02);
transform.rotate_x(drag.delta.y * 0.02);
}

12
release-content/migration-guides/observer_triggers.md Normal file
View File

@ -0,0 +1,12 @@
---
title: Observer Triggers
pull_requests: [19440]
---
Observers may be triggered on particular entities or globally.
Previously, a global trigger would claim to trigger on a particular `Entity`, `Entity::PLACEHOLDER`.
For correctness and transparency, triggers have been changed to `Option<Entity>`.
`Trigger::target` now returns `Option<Entity>` and `ObserverTrigger::target` is now of type `Option<Entity>`.
If you were checking for `Entity::PLACEHOLDER`, migrate to handling the `None` case.
If you were not checking for `Entity::PLACEHOLDER`, migrate to unwrapping, as `Entity::PLACEHOLDER` would have caused a panic before, at a later point.