feat(ecs): add relationships

1 files changed, 55 insertions, 0 deletions

diff --git a/ecs/examples/relationship.rs b/ecs/examples/relationship.rs
new file mode 100644
index 0000000..8610b47
--- /dev/null
+++ b/ecs/examples/relationship.rs
@@ -0,0 +1,55 @@
+use ecs::event::Event;
+use ecs::relationship::Relationship;
+use ecs::{Component, Query, World};
+
+#[derive(Component)]
+struct Sword
+{
+    attack_strength: u32,
+}
+
+#[derive(Component)]
+struct Player;
+
+#[derive(Component)]
+struct Health
+{
+    health: u32,
+}
+
+struct Holding;
+
+fn print_player_stats(player_query: Query<(Player, Health, Relationship<Holding, Sword>)>)
+{
+    for (_, health, sword_relationship) in &player_query {
+        println!("Player health: {}", health.health);
+
+        if let Some(sword) = sword_relationship.get() {
+            println!("Player sword attack strength: {}", sword.attack_strength);
+        }
+    }
+}
+
+#[derive(Debug)]
+struct Start;
+
+impl Event for Start {}
+
+fn main()
+{
+    let mut world = World::new();
+
+    world.register_system(Start, print_player_stats);
+
+    let sword_uid = world.create_entity((Sword { attack_strength: 17 },));
+
+    world.create_entity((
+        Player,
+        Health { health: 180 },
+        Relationship::<Holding, Sword>::new(&world, sword_uid),
+    ));
+
+    world.prepare();
+
+    world.emit(Start);
+}