1 files changed, 51 insertions, 0 deletions
diff --git a/Plugins/MonoGame.Extended/source/MonoGame.Extended.Entities/Systems/EntitySystem.cs b/Plugins/MonoGame.Extended/source/MonoGame.Extended.Entities/Systems/EntitySystem.cs
new file mode 100644
index 0000000..2c95107
--- /dev/null
+++ b/Plugins/MonoGame.Extended/source/MonoGame.Extended.Entities/Systems/EntitySystem.cs
@@ -0,0 +1,51 @@
+using MonoGame.Extended.Collections;
+
+namespace MonoGame.Extended.Entities.Systems
+{
+    public abstract class EntitySystem : ISystem
+    {
+        protected EntitySystem(AspectBuilder aspectBuilder)
+        {
+            _aspectBuilder = aspectBuilder;
+        }
+
+        public void Dispose()
+        {
+            if (_world != null)
+            {
+                _world.EntityManager.EntityAdded -= OnEntityAdded;
+                _world.EntityManager.EntityRemoved -= OnEntityRemoved;
+            }
+        }
+
+        private readonly AspectBuilder _aspectBuilder;
+        private EntitySubscription _subscription;
+
+        private World _world;
+
+        protected virtual void OnEntityChanged(int entityId) { }
+        protected virtual void OnEntityAdded(int entityId) { }
+        protected virtual void OnEntityRemoved(int entityId) { }
+
+        public Bag<int> ActiveEntities => _subscription.ActiveEntities;
+
+        public virtual void Initialize(World world)
+        {
+            _world = world;
+
+            var aspect = _aspectBuilder.Build(_world.ComponentManager);
+            _subscription = new EntitySubscription(_world.EntityManager, aspect);
+            _world.EntityManager.EntityAdded += OnEntityAdded;
+            _world.EntityManager.EntityRemoved += OnEntityRemoved;
+            _world.EntityManager.EntityChanged += OnEntityChanged;
+
+            Initialize(world.ComponentManager);
+        }
+
+        public abstract void Initialize(IComponentMapperService mapperService);
+
+        protected void DestroyEntity(int entityId) => _world.DestroyEntity(entityId);
+        protected Entity CreateEntity() => _world.CreateEntity();
+        protected Entity GetEntity(int entityId) => _world.GetEntity(entityId);
+    }
+}
+\ No newline at end of file