use observable collision events

to simplify key/head_drop collecting

src/head_drop.rs

@@ -4,7 +4,10 @@ use crate::{
     squish_animation::SquishAnimation, tb_entities::SecretHead,
 };
 use avian3d::prelude::*;
-use bevy::prelude::*;
+use bevy::{
+    ecs::{relationship::RelatedSpawner, spawn::SpawnWith},
+    prelude::*,
+};
 use std::f32::consts::PI;
 
 #[derive(Event, Reflect)]
@@ -44,7 +47,6 @@ struct SecretHeadMarker;
 pub struct HeadCollected(pub usize);
 
 pub fn plugin(app: &mut App) {
-    app.add_systems(Update, collect_head.run_if(in_state(GameState::Playing)));
     app.add_systems(OnEnter(GameState::Playing), spawn);
 
     global_observer!(app, on_head_drop);
@@ -85,6 +87,8 @@ fn on_head_drop(
     }
     .ok_or("asset not found")?;
 
+    let head_id = drop.head_id;
+
     commands
         .spawn((
             Name::new("headdrop"),
@@ -97,15 +101,18 @@ fn on_head_drop(
                 GameLayer::CollectiblePhysics,
                 LayerMask::ALL & !GameLayer::Player.to_bits(),
             ),
-            CollisionEventsEnabled,
             Restitution::new(0.6),
-            children![(
-                Collider::sphere(1.5),
-                CollisionLayers::new(GameLayer::CollectibleSensors, GameLayer::Player),
-                Sensor,
-                CollisionEventsEnabled,
-                HeadDrop(drop.head_id),
-            )],
+            Children::spawn(SpawnWith(move |parent: &mut RelatedSpawner<ChildOf>| {
+                parent
+                    .spawn((
+                        Collider::sphere(1.5),
+                        CollisionLayers::new(GameLayer::CollectibleSensors, GameLayer::Player),
+                        Sensor,
+                        CollisionEventsEnabled,
+                        HeadDrop(head_id),
+                    ))
+                    .observe(on_collect_head);
+            })),
         ))
         .insert_if(
             ExternalImpulse::new(spawn_dir * 180.).with_persistence(false),
@@ -120,23 +127,18 @@ fn on_head_drop(
     Ok(())
 }
 
-fn collect_head(
+fn on_collect_head(
+    trigger: Trigger<OnCollisionStart>,
     mut commands: Commands,
-    mut collision_event_reader: EventReader<CollisionStarted>,
     query_player: Query<&Player>,
     query_collectable: Query<(&HeadDrop, &ChildOf)>,
     query_secret: Query<&SecretHeadMarker>,
 ) {
-    for CollisionStarted(e1, e2) in collision_event_reader.read() {
-        let collectable = if query_player.contains(*e1) && query_collectable.contains(*e2) {
-            *e2
-        } else if query_player.contains(*e2) && query_collectable.contains(*e1) {
-            *e1
-        } else {
-            continue;
-        };
+    let collectable = trigger.target();
+    let collider = trigger.collider;
 
-        let (key, child_of) = query_collectable.get(collectable).unwrap();
+    if query_player.contains(collider) {
+        let (drop, child_of) = query_collectable.get(collectable).unwrap();
 
         let is_secret = query_secret.contains(collectable);
 
@@ -145,7 +147,8 @@ fn collect_head(
         } else {
             commands.trigger(PlaySound::HeadCollect);
         }
-        commands.trigger(HeadCollected(key.0));
+
+        commands.trigger(HeadCollected(drop.0));
         commands.entity(child_of.parent()).despawn();
     }
 }