Replace delete_the_dead with a system

chapter-07-damage/src/damage_system.rs

@@ -22,25 +22,30 @@ impl<'a> System<'a> for DamageSystem {
     }
 }
 
-pub fn delete_the_dead(ecs: &mut World) {
-    let mut dead: Vec<Entity> = Vec::new();
-    // Using a scope to make the borrow checker happy
-    {
-        let combat_stats = ecs.read_storage::<CombatStats>();
-        let players = ecs.read_storage::<Player>();
-        let entities = ecs.entities();
-        for (entity, stats) in (&entities, &combat_stats).join() {
+pub struct CleanupDead;
+
+impl<'a> System<'a> for CleanupDead {
+    type SystemData = (
+        Entities<'a>,
+        ReadStorage<'a, CombatStats>,
+        ReadStorage<'a, Player>,
+    );
+
+    fn run(&mut self, (entities, stats, player): Self::SystemData) {
+        let mut dead = Vec::new();
+
+        for (entity, stats) in (&entities, &stats).join() {
             if stats.hp < 1 {
-                let player = players.get(entity);
-                match player {
-                    None => dead.push(entity),
-                    Some(_) => console::log("You are dead"),
+                if player.contains(entity) {
+                    console::log("You are dead");
+                } else {
+                    dead.push(entity)
                 }
             }
         }
-    }
 
-    for victim in dead {
-        ecs.delete_entity(victim).expect("Unable to delete");
+        for e in dead {
+            entities.delete(e).expect("Unable to delete");
+        }
     }
 }

chapter-07-damage/src/main.rs

@@ -71,7 +71,7 @@ impl GameState for State {
             }
         }
         *self.ecs.write_resource() = newrunstate;
-        damage_system::delete_the_dead(&mut self.ecs);
+        damage_system::CleanupDead.run_now(&self.ecs);
 
         draw_map(&self.ecs, ctx);