feat(engine-ecs): add query traversal kind SelfOrUp

1 files changed, 44 insertions, 0 deletions

diff --git a/engine-ecs/examples/traversal.rs b/engine-ecs/examples/traversal.rs
new file mode 100644
index 0000000..23b1d6a
--- /dev/null
+++ b/engine-ecs/examples/traversal.rs
@@ -0,0 +1,44 @@
+use engine_ecs::pair::ChildOf;
+use engine_ecs::phase::START as START_PHASE;
+use engine_ecs::query::term::{Traverse, TraverseSelfOrUp};
+use engine_ecs::{pair, Component, Query, World};
+
+#[derive(Component)]
+struct SomeData
+{
+    num: u64,
+}
+
+#[derive(Component)]
+struct Greeting
+{
+    greeting: String,
+}
+
+fn say_hello(query: Query<(Traverse<(&Greeting,), TraverseSelfOrUp, ChildOf>, &SomeData)>)
+{
+    for (greeting, data) in &query {
+        println!("{}: {}", greeting.greeting, data.num);
+    }
+}
+
+fn main()
+{
+    let mut world = World::new();
+
+    world.register_system(*START_PHASE, say_hello);
+
+    let parent_ent = world.spawn((Greeting {
+        greeting: "Good afternoon".to_string(),
+    },));
+
+    world.spawn((SomeData { num: 345 }, pair!(ChildOf, { parent_ent })));
+
+    world.spawn((
+        SomeData { num: 123 },
+        Greeting { greeting: "Good evening".to_string() },
+        pair!(ChildOf, { parent_ent }),
+    ));
+
+    world.step();
+}