feat(ecs): add support for pairs with target component as data

2 files changed, 57 insertions, 2 deletions

diff --git a/ecs/examples/component_relationship.rs b/ecs/examples/component_relationship.rs
new file mode 100644
index 0000000..4453e3a
--- /dev/null
+++ b/ecs/examples/component_relationship.rs
@@ -0,0 +1,56 @@
+use ecs::pair::Pair;
+use ecs::phase::START as START_PHASE;
+use ecs::{Component, Query, World};
+
+#[derive(Component)]
+struct Person
+{
+    name: String,
+}
+
+fn print_dog_likers(query: Query<(&Person, Pair<Likes, &Dogs>)>)
+{
+    for (person, liked_dogs) in &query {
+        println!(
+            "{} likes {} dogs!",
+            person.name,
+            if liked_dogs.large { "large" } else { "small" },
+        );
+    }
+}
+
+#[derive(Component)]
+struct Likes;
+
+#[derive(Component)]
+struct Cats;
+
+#[derive(Component)]
+struct Dogs
+{
+    large: bool,
+}
+
+fn main()
+{
+    let mut world = World::new();
+
+    world.register_system(*START_PHASE, print_dog_likers);
+
+    world.create_entity((
+        Person { name: "Irving".to_string() },
+        Pair::new_with_comp_target::<Likes>(Dogs { large: true }),
+    ));
+
+    world.create_entity((
+        Person { name: "Mark".to_string() },
+        Pair::new_with_comp_target::<Likes>(Cats),
+    ));
+
+    world.create_entity((
+        Person { name: "Helena".to_string() },
+        Pair::new_with_comp_target::<Likes>(Dogs { large: false }),
+    ));
+
+    world.step();
+}
diff --git a/ecs/examples/relationship.rs b/ecs/examples/relationship.rs
index b607398..f99d090 100644
--- a/ecs/examples/relationship.rs
+++ b/ecs/examples/relationship.rs
@@ -1,6 +1,5 @@
-use ecs::pair::Pair;
+use ecs::pair::{Pair, Wildcard};
 use ecs::phase::START as START_PHASE;
-use ecs::uid::Wildcard;
 use ecs::{Component, Query, World};
 
 #[derive(Component)]