resources

src/main.rs

@@ -20,9 +20,14 @@ fn add_people(mut commands: Commands) {
     commands.spawn((Person, Name("Zayna Nieves".to_string())));
 }
 
-fn greet_people(query: Query<&Name, With<Person>>) {
-    for name in &query {
-        println!("hello {}!", name.0);
+#[derive(Resource)]
+struct GreetTimer(Timer);
+
+fn greet_people(time: Res<Time>, mut timer: ResMut<GreetTimer>, query: Query<&Name, With<Person>>) {
+    if timer.0.tick(time.delta()).just_finished() {
+        for name in &query {
+            println!("hello {}!", name.0);
+        }
     }
 }
 
@@ -30,7 +35,8 @@ pub struct HelloPlugin;
 
 impl Plugin for HelloPlugin {
     fn build(&self, app: &mut App) {
-        app.add_systems(Startup, add_people)
-            .add_systems(Update, (hello_world, greet_people).chain());
+        app.insert_resource(GreetTimer(Timer::from_seconds(2.0, TimerMode::Repeating)))
+            .add_systems(Startup, add_people)
+            .add_systems(Update, greet_people);
     }
 }