1 files changed, 85 insertions, 0 deletions
diff --git a/engine-ecs/examples/multiple_queries.rs b/engine-ecs/examples/multiple_queries.rs
new file mode 100644
index 0000000..1a4aaad
--- /dev/null
+++ b/engine-ecs/examples/multiple_queries.rs
@@ -0,0 +1,85 @@
+use std::fmt::Display;
+
+use engine_ecs::phase::START as START_PHASE;
+use engine_ecs::{Component, Query, World};
+
+#[derive(Component)]
+struct Health
+{
+    health: u32,
+}
+
+#[derive(Component)]
+enum AttackStrength
+{
+    Strong,
+    Weak,
+}
+
+#[derive(Component)]
+struct EnemyName
+{
+    name: String,
+}
+
+impl Display for EnemyName
+{
+    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result
+    {
+        self.name.fmt(formatter)
+    }
+}
+
+fn do_attacks(
+    attacker_query: Query<(&AttackStrength,)>,
+    enemy_query: Query<(&mut Health, &EnemyName)>,
+)
+{
+    for (attack_strength,) in &attacker_query {
+        for (mut health, enemy_name) in &enemy_query {
+            let damage = match *attack_strength {
+                AttackStrength::Strong => 20,
+                AttackStrength::Weak => 10,
+            };
+
+            if health.health <= damage {
+                println!("Enemy '{}' died", *enemy_name);
+
+                health.health = 0;
+
+                continue;
+            }
+
+            health.health -= damage;
+
+            println!("Enemy '{}' took {damage} damage", *enemy_name);
+        }
+    }
+}
+
+fn main()
+{
+    let mut world = World::new();
+
+    world.register_system(*START_PHASE, do_attacks);
+
+    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.step();
+}