feat(ecs): emit Removed events before component removal

2 files changed, 80 insertions, 3 deletions

diff --git a/ecs/examples/component_events.rs b/ecs/examples/component_events.rs
new file mode 100644
index 0000000..4e7335f
--- /dev/null
+++ b/ecs/examples/component_events.rs
@@ -0,0 +1,68 @@
+use ecs::actions::Actions;
+use ecs::component::Component;
+use ecs::event::component::{Changed, Removed};
+use ecs::pair::Pair;
+use ecs::phase::UPDATE;
+use ecs::system::observer::Observe;
+use ecs::{Component, Query, World};
+
+#[derive(Debug, Component)]
+struct CheeseCrumbs
+{
+    cnt: usize,
+}
+
+#[derive(Debug, Component)]
+struct Cheese
+{
+    name: &'static str,
+}
+
+fn eat_cheese(query: Query<(&Cheese, &mut CheeseCrumbs)>, mut actions: Actions)
+{
+    for (cheese_ent_id, (_, mut cheese_crumbs)) in query.iter_with_euids() {
+        println!("Eating cheese!");
+
+        cheese_crumbs.cnt += 40;
+        cheese_crumbs.set_changed();
+
+        actions.remove_components(cheese_ent_id, [Cheese::id()]);
+    }
+}
+
+fn on_cheese_removed(observe: Observe<Pair<Removed, Cheese>>)
+{
+    for evt_match in &observe {
+        let ent = evt_match.get_entity().unwrap();
+
+        let cheese = ent.get::<Cheese>().unwrap();
+
+        println!("{} cheese was eaten", cheese.name);
+    }
+}
+
+fn on_cheese_crumbs_changed(observe: Observe<Pair<Changed, CheeseCrumbs>>)
+{
+    for evt_match in &observe {
+        let ent = evt_match.get_entity().unwrap();
+
+        let cheese_crumbs = ent.get::<CheeseCrumbs>().unwrap();
+
+        println!("Cheese crumbs count changed to {}", cheese_crumbs.cnt);
+    }
+}
+
+fn main()
+{
+    let mut world = World::new();
+
+    world.register_system(*UPDATE, eat_cheese);
+    world.register_observer(on_cheese_removed);
+    world.register_observer(on_cheese_crumbs_changed);
+
+    world.create_entity((Cheese { name: "Brie" }, CheeseCrumbs { cnt: 0 }));
+    world.create_entity((Cheese { name: "Parmesan" }, CheeseCrumbs { cnt: 0 }));
+    world.create_entity((Cheese { name: "Gouda" }, CheeseCrumbs { cnt: 0 }));
+
+    world.step();
+}
diff --git a/ecs/examples/component_removed_event.rs b/ecs/examples/component_removed_event.rs
index e8d1a47..f984092 100644
--- a/ecs/examples/component_removed_event.rs
+++ b/ecs/examples/component_removed_event.rs
@@ -7,7 +7,10 @@ use ecs::system::observer::Observe;
 use ecs::{Component, Query, World};
 
 #[derive(Debug, Component)]
-struct Cheese;
+struct Cheese
+{
+    name: &'static str,
+}
 
 fn eat_cheese(query: Query<(&Cheese,)>, mut actions: Actions)
 {
@@ -21,7 +24,11 @@ fn eat_cheese(query: Query<(&Cheese,)>, mut actions: Actions)
 fn on_cheese_removed(observe: Observe<Pair<Removed, Cheese>>)
 {
     for evt_match in &observe {
-        println!("Cheese entity {} was eaten", evt_match.id());
+        let ent = evt_match.get_entity().unwrap();
+
+        let cheese = ent.get::<Cheese>().unwrap();
+
+        println!("{} cheese was eaten", cheese.name);
     }
 }
 
@@ -32,7 +39,9 @@ fn main()
     world.register_system(*UPDATE, eat_cheese);
     world.register_observer(on_cheese_removed);
 
-    world.create_entity((Cheese,));
+    world.create_entity((Cheese { name: "Brie" },));
+    world.create_entity((Cheese { name: "Parmesan" },));
+    world.create_entity((Cheese { name: "Gouda" },));
 
     world.step();
     world.step();