5 files changed, 75 insertions, 32 deletions

diff --git a/ecs/examples/multiple_queries.rs b/ecs/examples/multiple_queries.rs
index 9a699c2..ed02a69 100644
--- a/ecs/examples/multiple_queries.rs
+++ b/ecs/examples/multiple_queries.rs
@@ -1,5 +1,6 @@
 use std::fmt::Display;
 
+use ecs::event::{Event, Id as EventId};
 use ecs::{Component, Query, World};
 
 #[derive(Component)]
@@ -57,16 +58,21 @@ fn do_attacks(
 }
 
 #[derive(Debug, PartialEq, Eq, Hash)]
-enum Event
+struct Start;
+
+impl Event for Start
 {
-    Start,
+    fn id(&self) -> EventId
+    {
+        EventId::of::<Self>()
+    }
 }
 
 fn main()
 {
-    let mut world = World::<Event>::new();
+    let mut world = World::new();
 
-    world.register_system(Event::Start, do_attacks);
+    world.register_system(&Start, do_attacks);
 
     world.create_entity((
         Health { health: 100 },
@@ -86,5 +92,5 @@ fn main()
     world.create_entity((AttackStrength::Strong,));
     world.create_entity((AttackStrength::Weak,));
 
-    world.emit(&Event::Start);
+    world.emit(&Start);
 }
diff --git a/ecs/examples/simple.rs b/ecs/examples/simple.rs
index 76d9538..9983c4a 100644
--- a/ecs/examples/simple.rs
+++ b/ecs/examples/simple.rs
@@ -1,3 +1,4 @@
+use ecs::event::{Event, Id as EventId};
 use ecs::{Component, Query, World};
 
 #[derive(Component)]
@@ -19,17 +20,22 @@ fn say_hello(query: Query<(SomeData, Greeting)>)
     }
 }
 
-#[derive(Debug, PartialEq, Eq, Hash)]
-enum Event
+#[derive(Debug)]
+struct Start;
+
+impl Event for Start
 {
-    Start,
+    fn id(&self) -> EventId
+    {
+        EventId::of::<Self>()
+    }
 }
 
 fn main()
 {
-    let mut world = World::<Event>::new();
+    let mut world = World::new();
 
-    world.register_system(Event::Start, say_hello);
+    world.register_system(&Start, say_hello);
 
     world.create_entity((
         SomeData { num: 987_654 },
@@ -43,5 +49,5 @@ fn main()
         Greeting { greeting: "Good evening".to_string() },
     ));
 
-    world.emit(&Event::Start);
+    world.emit(&Start);
 }
diff --git a/ecs/examples/with_local.rs b/ecs/examples/with_local.rs
index b37a5c3..0342930 100644
--- a/ecs/examples/with_local.rs
+++ b/ecs/examples/with_local.rs
@@ -1,4 +1,5 @@
 use ecs::component::Local;
+use ecs::event::{Event, Id as EventId};
 use ecs::system::{Into, System};
 use ecs::{Component, Query, World};
 
@@ -41,25 +42,30 @@ fn say_whats_up(query: Query<(SomeData, Name)>, mut state: Local<SayHelloState>)
     }
 }
 
-#[derive(Debug, PartialEq, Eq, Hash)]
-enum Event
+#[derive(Debug)]
+struct Update;
+
+impl Event for Update
 {
-    Update,
+    fn id(&self) -> EventId
+    {
+        EventId::of::<Self>()
+    }
 }
 
 fn main()
 {
-    let mut world = World::<Event>::new();
+    let mut world = World::new();
 
     world.register_system(
-        Event::Update,
+        &Update,
         say_hello
             .into_system()
             .initialize((SayHelloState { cnt: 0 },)),
     );
 
     world.register_system(
-        Event::Update,
+        &Update,
         say_whats_up
             .into_system()
             .initialize((SayHelloState { cnt: 0 },)),
@@ -69,9 +75,9 @@ fn main()
 
     world.create_entity((SomeData { num: 345 },));
 
-    world.emit(&Event::Update);
+    world.emit(&Update);
 
     println!("Haha");
 
-    world.emit(&Event::Update);
+    world.emit(&Update);
 }
diff --git a/ecs/src/event.rs b/ecs/src/event.rs
new file mode 100644
index 0000000..0cf6da7
--- /dev/null
+++ b/ecs/src/event.rs
@@ -0,0 +1,24 @@
+use std::any::TypeId;
+use std::fmt::Debug;
+use std::hash::Hash;
+
+pub trait Event: Debug + 'static
+{
+    fn id(&self) -> Id;
+}
+
+/// The ID of a [`Event`].
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct Id
+{
+    inner: TypeId,
+}
+
+impl Id
+{
+    /// Returns the id of a [`Event`];
+    pub fn of<EventT: Event>() -> Self
+    {
+        Self { inner: TypeId::of::<EventT>() }
+    }
+}
diff --git a/ecs/src/lib.rs b/ecs/src/lib.rs
index a9ef2a4..e22913f 100644
--- a/ecs/src/lib.rs
+++ b/ecs/src/lib.rs
@@ -3,11 +3,11 @@
 use std::any::{Any, TypeId};
 use std::collections::{HashMap, HashSet};
 use std::fmt::Debug;
-use std::hash::Hash;
 use std::marker::PhantomData;
 use std::slice::{Iter as SliceIter, IterMut as SliceIterMut};
 
 use crate::component::{Component, Sequence as ComponentSequence};
+use crate::event::{Event, Id as EventId};
 use crate::system::{
     NoInitParamFlag as NoInitSystemParamFlag,
     Param as SystemParam,
@@ -17,6 +17,7 @@ use crate::system::{
 use crate::tuple::FilterExclude as TupleFilterExclude;
 
 pub mod component;
+pub mod event;
 pub mod system;
 pub mod tuple;
 
@@ -29,14 +30,14 @@ struct Entity
 }
 
 #[derive(Debug)]
-pub struct World<Event>
+pub struct World
 {
     systems: Vec<TypeErasedSystem>,
-    events: HashMap<Event, Vec<usize>>,
+    events: HashMap<EventId, Vec<usize>>,
     component_storage: ComponentStorage,
 }
 
-impl<Event> World<Event>
+impl World
 {
     #[must_use]
     pub fn new() -> Self
@@ -57,15 +58,17 @@ impl<Event> World<Event>
             .push(Entity { components: components.into_vec() });
     }
 
-    pub fn register_system<TSystem, SystemImpl>(&mut self, event: Event, system: TSystem)
-    where
-        Event: Hash + PartialEq + Eq,
+    pub fn register_system<TSystem, SystemImpl>(
+        &mut self,
+        event: &impl Event,
+        system: TSystem,
+    ) where
         TSystem: System<SystemImpl>,
     {
         self.systems.push(system.into_type_erased());
 
         self.events
-            .entry(event)
+            .entry(event.id())
             .or_default()
             .push(self.systems.len() - 1);
     }
@@ -75,11 +78,9 @@ impl<Event> World<Event>
     ///
     /// # Panics
     /// Will panic if a system has dissapeared.
-    pub fn emit(&mut self, event: &Event)
-    where
-        Event: Hash + PartialEq + Eq,
+    pub fn emit(&mut self, event: &impl Event)
     {
-        let Some(system_indices) = self.events.get(event).cloned() else {
+        let Some(system_indices) = self.events.get(&event.id()).cloned() else {
             return;
         };
 
@@ -98,7 +99,7 @@ impl<Event> World<Event>
     }
 }
 
-impl<Event> Default for World<Event>
+impl Default for World
 {
     fn default() -> Self
     {