refactor: Fixed Compiler Warning On Possible Null

Engine.Core/GameManager.cs

@@ -19,7 +19,7 @@ public class GameManager : IEntity
 
 
     private IList<IGameObject> _gameObjects = new List<IGameObject>(Constants.GAME_OBJECTS_SIZE_INITIAL);
-    private IList<IDrawable> _drawables = new List<IDrawable>(Constants.DRAWABLE_OBJECTS_SIZE_INITIAL);
+    private IList<IDisplayable> _drawables = new List<IDisplayable>(Constants.DRAWABLE_OBJECTS_SIZE_INITIAL);
 
     private IStateEnable _stateEnable = null!;
     private GameObjectFactory _gameObjectFactory = null!;
@@ -37,12 +37,25 @@ public class GameManager : IEntity
 
     public bool Initialized => _initialized;
     public IList<IGameObject> GameObjects => _gameObjects;
-    public IStateEnable StateEnable { get { if (_stateEnable is null) Assign(new StateEnableFactory().Instantiate(this)); return _stateEnable; } }
+    public IStateEnable StateEnable
+    {
+        get
+        {
+            if (_stateEnable is null)
+            {
+                Assign(new StateEnableFactory().Instantiate(this));
+                if (_stateEnable is null)
+                    throw NotAssignedException.From(this, _stateEnable);
+            }
+
+            return _stateEnable;
+        }
+    }
 
     public void RegisterGameObject(IGameObject gameObject)
     {
         if (_gameObjects.Contains(gameObject))
-            throw new Exception($"{nameof(IGameComponent)} named {gameObject.Name} is already registered to the {nameof(GameManager)}.");
+            throw new Exception($"{nameof(IGameObject)} named {gameObject.Name} is already registered to the {nameof(GameManager)}.");
 
         Register(gameObject);
     }
@@ -57,7 +70,7 @@ public class GameManager : IEntity
     public IGameObject RemoveGameObject(IGameObject gameObject)
     {
         if (!_gameObjects.Contains(gameObject))
-            throw new Exception($"{nameof(IGameComponent)} named {gameObject.Name} is not registered to the {nameof(GameManager)}.");
+            throw new Exception($"{nameof(IGameObject)} named {gameObject.Name} is not registered to the {nameof(GameManager)}.");
 
         Unregister(gameObject);
         return gameObject;
@@ -125,9 +138,8 @@ public class GameManager : IEntity
     {
         spriteBatch.Begin();
 
-        foreach (var gameObject in GameObjects)
+        foreach (var drawable in _drawables)
-            if (gameObject.BehaviourController.TryGetBehaviour<IDisplayable>(out var drawable))
+            drawable.Draw(spriteBatch);
-                drawable.Draw(spriteBatch);
 
         spriteBatch.End();
     }
@@ -140,7 +152,7 @@ public class GameManager : IEntity
         gameObject.BehaviourController.OnBehaviourRemoved -= OnBehaviourRemove;
         gameObject.OnFinalized -= OnGameObjectFinalize;
 
-        if (gameObject.BehaviourController.TryGetBehaviour<IDrawable>(out var drawable))
+        if (gameObject.BehaviourController.TryGetBehaviour<IDisplayable>(out var drawable))
             _drawables.Remove(drawable);
 
         _gameObjects.Remove(gameObject);
@@ -152,7 +164,7 @@ public class GameManager : IEntity
         gameObject.BehaviourController.OnBehaviourRemoved += OnBehaviourRemove;
         gameObject.OnFinalized += OnGameObjectFinalize;
 
-        if (gameObject.BehaviourController.TryGetBehaviour<IDrawable>(out var drawable))
+        if (gameObject.BehaviourController.TryGetBehaviour<IDisplayable>(out var drawable))
             _drawables.Add(drawable);
 
         _gameObjects.Add(gameObject);
@@ -166,13 +178,13 @@ public class GameManager : IEntity
 
     private void OnBehaviourAdd(IBehaviourController controller, IBehaviour behaviour)
     {
-        if (behaviour is IDrawable drawable)
+        if (behaviour is IDisplayable drawable)
             _drawables.Add(drawable);
     }
 
     private void OnBehaviourRemove(IBehaviourController controller, IBehaviour behaviour)
     {
-        if (behaviour is IDrawable drawable)
+        if (behaviour is IDisplayable drawable)
             _drawables.Remove(drawable);
     }
 }