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Co-authored-by: Alice Cecile <[email protected]>

examples/README.md

@@ -159,7 +159,7 @@ Example | File | Description
 `component_change_detection` | [`ecs/component_change_detection.rs`](./ecs/component_change_detection.rs) | Change detection on components
 `event` | [`ecs/event.rs`](./ecs/event.rs) | Illustrates event creation, activation, and reception
 `fixed_timestep` | [`ecs/fixed_timestep.rs`](./ecs/fixed_timestep.rs) | Shows how to create systems that run every fixed timestep, rather than every tick
-`generic_system` | [`ecs/generic_system.rs`](./ecs/generic_system.rs) | Shows how to create generic systems
+`generic_system` | [`ecs/generic_system.rs`](./ecs/generic_system.rs) | Shows how to create systems that can be reused with different types
 `hierarchy` | [`ecs/hierarchy.rs`](./ecs/hierarchy.rs) | Creates a hierarchy of parents and children entities
 `iter_combinations` | [`ecs/iter_combinations.rs`](./ecs/iter_combinations.rs) | Shows how to iterate over combinations of query results.
 `parallel_query` | [`ecs/parallel_query.rs`](./ecs/parallel_query.rs) | Illustrates parallel queries with `ParallelIterator`

examples/ecs/generic_system.rs

@@ -20,6 +20,7 @@ fn main() {
         .add_system_set(SystemSet::on_update(AppState::MainMenu).with_system(transition_to_in_game))
         // add the cleanup systems
         .add_system_set(
+            // Pass in the types your system should operate on using the ::<T> (turbofish) syntax
             SystemSet::on_exit(AppState::MainMenu).with_system(cleanup_system::<MenuClose>),
         )
         .add_system_set(
@@ -58,6 +59,8 @@ fn transition_to_in_game(mut state: ResMut<State<AppState>>, keyboard_input: Res
     }
 }
 
+// Type arguments on functions come after the function name, but before ordinary arguments.
+// Here, the `Component` trait is a trait bound on T, our generic type
 fn cleanup_system<T: Component>(mut commands: Commands, query: Query<Entity, With<T>>) {
     for e in query.iter() {
         commands.entity(e).despawn_recursive();