feat(ecs): add support for multiple system queries & local components

1 files changed, 87 insertions, 0 deletions

diff --git a/ecs/examples/multiple_queries.rs b/ecs/examples/multiple_queries.rs
new file mode 100644
index 0000000..a4a5d2d
--- /dev/null
+++ b/ecs/examples/multiple_queries.rs
@@ -0,0 +1,87 @@
+use std::fmt::Display;
+
+use ecs::{Query, World};
+
+struct Health
+{
+    health: u32,
+}
+
+enum AttackStrength
+{
+    Strong,
+    Weak,
+}
+
+struct EnemyName
+{
+    name: String,
+}
+
+impl Display for EnemyName
+{
+    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result
+    {
+        self.name.fmt(formatter)
+    }
+}
+
+fn say_hello(
+    mut query: Query<(AttackStrength,)>,
+    mut enemy_query: Query<(Health, EnemyName)>,
+)
+{
+    for (attack_strength,) in query.iter_mut() {
+        for (health, enemy_name) in enemy_query.iter_mut() {
+            let damage = match attack_strength {
+                AttackStrength::Strong => 20,
+                AttackStrength::Weak => 10,
+            };
+
+            if health.health <= damage {
+                println!("Enemy '{enemy_name}' died");
+
+                health.health = 0;
+
+                continue;
+            }
+
+            health.health -= damage;
+
+            println!("Enemy '{enemy_name}' took {damage} damage");
+        }
+    }
+}
+
+#[derive(Debug, PartialEq, Eq, Hash)]
+enum Event
+{
+    Start,
+}
+
+fn main()
+{
+    let mut world = World::<Event>::new();
+
+    world.register_system(Event::Start, say_hello);
+
+    world.create_entity((
+        Health { health: 100 },
+        EnemyName { name: "Big spider".to_string() },
+    ));
+
+    world.create_entity((
+        Health { health: 30 },
+        EnemyName { name: "Small goblin".to_string() },
+    ));
+
+    world.create_entity((
+        Health { health: 30 },
+        EnemyName { name: "Headcrab".to_string() },
+    ));
+
+    world.create_entity((AttackStrength::Strong,));
+    world.create_entity((AttackStrength::Weak,));
+
+    world.emit(&Event::Start);
+}