Assets/Scenes/M2Scene.shade

@@ -256,4 +256,7 @@
       Color: {x: 1, y: 1, z: 1, w: 1}
       Layer: 4294967295
       Strength: 0.25
-  Scripts: ~
+  Scripts:
+    - Type: PickAndThrow
+      throwForce: [100, 200, 100]
+      item: 1

SHADE_Engine/src/Editor/SHEditorUI.cpp

@@ -288,7 +288,7 @@ namespace SHADE
     return CHANGED;
   }
 
-  bool SHEditorUI::InputGameObjectField(const std::string& label, uint32_t& value, bool* isHovered)
+  bool SHEditorUI::InputGameObjectField(const std::string& label, uint32_t& value, bool* isHovered, bool alwaysNull)
   {
     ImGui::Text(label.c_str());
     if (isHovered)
@@ -296,7 +296,7 @@ namespace SHADE
     ImGui::SameLine();
     SHEntity* entity = SHEntityManager::GetEntityByID(value);
     std::ostringstream oss;
-    if (entity)
+    if (!alwaysNull && entity)
     {
       oss << value << ": " << entity->name;
     }
@@ -314,6 +314,13 @@ namespace SHADE
         SHDragDrop::EndTarget();
       }
     }
+    ImGui::SameLine();
+    if (ImGui::Button("Clear"))
+    {
+      value = MAX_EID;
+      changed = true;
+    }
+
     return changed;
   }
 

SHADE_Engine/src/Editor/SHEditorUI.h

@@ -313,8 +313,12 @@ namespace SHADE
     /// <param name="label">Label used to identify this widget.</param>
     /// <param name="value">Reference to the variable to store the result.</param>
     /// <param name="isHovered>If set, stores the hover state of this widget.</param>
+    /// <param name="alwaysNull>
+    /// If set, the field displayed will always be blank regardless of specified 
+    /// GameObject.
+    /// </param>
     /// <returns>True if the value was changed.</returns>
-    static bool InputGameObjectField(const std::string& label, uint32_t& value, bool* isHovered = nullptr);
+    static bool InputGameObjectField(const std::string& label, uint32_t& value, bool* isHovered = nullptr, bool alwaysNull = false);
     /// <summary>
     /// Creates a combo box for enumeration input.
     /// </summary>

SHADE_Managed/src/Editor/Editor.cxx

@@ -290,9 +290,14 @@ namespace SHADE
         {
             GameObject gameObj = safe_cast<GameObject>(field->GetValue(object));
             uint32_t entityId = gameObj.GetEntity();
-            if (SHEditorUI::InputGameObjectField(Convert::ToNative(field->Name), entityId, &isHovered))
+            if (SHEditorUI::InputGameObjectField(Convert::ToNative(field->Name), entityId, &isHovered, !gameObj))
             {
                 GameObject newVal = GameObject(entityId);
+                if (entityId != MAX_EID)
+                {
+                    // Null GameObject set
+                    newVal = GameObject(entityId);
+                }
                 field->SetValue(object, newVal);
                 registerUndoAction(object, field, newVal, gameObj);
             }

SHADE_Managed/src/Engine/GameObject.cxx

@@ -36,6 +36,8 @@ namespace SHADE
 
     void GameObject::Destroy(GameObject obj)
     {
+        if (!obj.valid)
+            throw gcnew System::NullReferenceException("Attempted to destroy a null GameObject.");
         SHEntityManager::DestroyEntity(static_cast<EntityID>(obj.GetEntity()));
     }
 
@@ -56,15 +58,21 @@ namespace SHADE
     /*---------------------------------------------------------------------------------*/
     System::String^ GameObject::Name::get()
     {
+        if (!valid)
+            throw gcnew System::NullReferenceException();
         return Convert::ToCLI(GetNativeEntity().name);
 
     }
     bool GameObject::IsActiveSelf::get()
     {
+        if (!valid)
+            throw gcnew System::NullReferenceException();
         return GetNativeEntity().GetActive();
     }
     bool GameObject::IsActiveInHierarchy::get()
     {
+        if (!valid)
+            throw gcnew System::NullReferenceException();
         auto node = SHSceneManager::GetCurrentSceneGraph().GetNode(GetEntity());
         if (!node)
         {
@@ -75,10 +83,14 @@ namespace SHADE
     }
     Entity GameObject::EntityId::get()
     {
+        if (!valid)
+            throw gcnew System::NullReferenceException();
         return entity;
     }
     GameObject^ GameObject::Parent::get()
     {
+        if (!valid)
+            throw gcnew System::NullReferenceException();
         const auto& SCENE_GRAPH = SHSceneManager::GetCurrentSceneGraph();
         const auto* ROOT = SCENE_GRAPH.GetRoot();
 
@@ -91,6 +103,8 @@ namespace SHADE
     }
     void GameObject::Parent::set(GameObject^ newParent)
     {
+        if (!valid)
+            throw gcnew System::NullReferenceException();
         const auto& SCENE_GRAPH = SHSceneManager::GetCurrentSceneGraph();
 
         if (newParent == nullptr)
@@ -104,10 +118,14 @@ namespace SHADE
     /*---------------------------------------------------------------------------------*/
     void GameObject::SetName(System::String^ name)
     {
+        if (!valid)
+            throw gcnew System::NullReferenceException();
         GetNativeEntity().name = Convert::ToNative(name);
     }
     void GameObject::SetActive(bool active)
     {
+        if (!valid)
+            throw gcnew System::NullReferenceException();
         GetNativeEntity().SetActive(active);
     }
 
@@ -117,30 +135,40 @@ namespace SHADE
     generic <typename T>
     T GameObject::AddComponent()
     {
+        if (!valid)
+            throw gcnew System::NullReferenceException();
         return ECS::AddComponent<T>(entity);
     }
 
     generic <typename T>
     T GameObject::GetComponent()
     {
+        if (!valid)
+            throw gcnew System::NullReferenceException();
         return ECS::GetComponent<T>(entity);
     }
 
     generic <typename T>
     T GameObject::GetComponentInChildren()
     {
+        if (!valid)
+            throw gcnew System::NullReferenceException();
         return ECS::GetComponentInChildren<T>(entity);
     }
 
     generic <typename T>
     T GameObject::EnsureComponent()
     {
+        if (!valid)
+            throw gcnew System::NullReferenceException();
         return ECS::EnsureComponent<T>(entity);
     }
 
     generic <typename T>
     void GameObject::RemoveComponent()
     {
+        if (!valid)
+            throw gcnew System::NullReferenceException();
         ECS::RemoveComponent<T>(entity);
     }
 
@@ -150,30 +178,40 @@ namespace SHADE
     generic <typename T>
     T GameObject::AddScript()
     {
+        if (!valid)
+            throw gcnew System::NullReferenceException();
         return ScriptStore::AddScript<T>(entity);
     }
 
     generic <typename T>
     T GameObject::GetScript()
     {
+        if (!valid)
+            throw gcnew System::NullReferenceException();
         return ScriptStore::GetScript<T>(entity);
     }
 
     generic <typename T>
     T GameObject::GetScriptInChildren()
     {
+        if (!valid)
+            throw gcnew System::NullReferenceException();
         return ScriptStore::GetScriptInChildren<T>(entity);
     }
 
     generic <typename T>
     System::Collections::Generic::IEnumerable<T>^ GameObject::GetScripts()
     {
+        if (!valid)
+            throw gcnew System::NullReferenceException();
         return ScriptStore::GetScripts<T>(entity);
     }
 
     generic <typename T>
     void GameObject::RemoveScript()
     {
+        if (!valid)
+            throw gcnew System::NullReferenceException();
         ScriptStore::RemoveScript<T>(entity);
     }
 
@@ -183,11 +221,13 @@ namespace SHADE
     GameObject::GameObject(const SHEntity& entity)
         : entity{ entity.GetEID() }
         , children{ gcnew System::Collections::ArrayList }
+        , valid{ true }
     {}
 
     GameObject::GameObject(Entity entity)
         : entity{ entity }
         , children{ gcnew System::Collections::ArrayList }
+        , valid{ true }
     {}
 
     /*---------------------------------------------------------------------------------*/
@@ -195,6 +235,8 @@ namespace SHADE
     /*---------------------------------------------------------------------------------*/
     SHEntity& GameObject::GetNativeEntity()
     {
+        if (!valid)
+            throw gcnew System::NullReferenceException();
         SHEntity* nativeEntity = SHEntityManager::GetEntityByID(entity);
         if (nativeEntity == nullptr)
             throw gcnew System::InvalidOperationException("[GameObject] Unable to obtain native Entity for GameObject.");
@@ -202,12 +244,20 @@ namespace SHADE
         return *nativeEntity;
     }
 
+    /*---------------------------------------------------------------------------------*/
+    /* Operator Overloads                                                              */
+    /*---------------------------------------------------------------------------------*/
+    GameObject::operator bool(GameObject gameObj)
+    {
+        return gameObj.valid;
+    }
+
     /*---------------------------------------------------------------------------------*/
     /* IEquatable                                                                      */
     /*---------------------------------------------------------------------------------*/
     bool GameObject::Equals(GameObject other)
     {
-        return entity == other.entity;
+        return (!valid && !other.valid) || entity == other.entity;
     }
 
     /*---------------------------------------------------------------------------------*/

SHADE_Managed/src/Engine/GameObject.hxx

@@ -29,8 +29,9 @@ namespace SHADE
     /* Class Definitions                                                               */
     /*---------------------------------------------------------------------------------*/
     /// <summary>
-    /// Lightweight object for an PlushieEngine Entity that allows for easy access 
+    /// Lightweight object for an Entity that allows for easy access to Component and 
-    /// to Component and Script operations.
+    /// Script operations.
+    /// Can be set to a invalid/null GameObject by default construction.
     /// </summary>
     public value class GameObject : public System::IEquatable<GameObject>
     {
@@ -247,12 +248,22 @@ namespace SHADE
         /// <returns>Native Entity object that this GameObject represents.</returns>
         SHEntity& GetNativeEntity();
 
+        /*-----------------------------------------------------------------------------*/
+        /* Operator Overloads                                                          */
+        /*-----------------------------------------------------------------------------*/
+        /// <summary>
+        /// Implicit conversion operator to enable checking if a GameObject is valid.
+        /// </summary>
+        /// <param name="gameObj">GameObjects to check.</param>
+        static operator bool(GameObject gameObj);
+
       private:
         /*-----------------------------------------------------------------------------*/
         /* Data Members                                                                */
         /*-----------------------------------------------------------------------------*/
         Entity                            entity;
         System::Collections::ArrayList^   children;
+        bool                              valid;
 
       public:
         /*-----------------------------------------------------------------------------*/

SHADE_Managed/src/Serialisation/ReflectionUtilities.cxx

@@ -171,7 +171,7 @@ namespace SHADE
             else if (fieldInfo->FieldType == GameObject::typeid)
             {
                 GameObject gameObj = safe_cast<GameObject>(fieldInfo->GetValue(object));
-                fieldNode = gameObj.GetEntity();
+                fieldNode = gameObj ? gameObj.GetEntity() : MAX_EID;
             }
             else // Not any of the supported types
             {
@@ -250,7 +250,8 @@ namespace SHADE
         }
         else if (fieldInfo->FieldType == GameObject::typeid)
         {
-            fieldInfo->SetValue(object, GameObject(node.as<uint32_t>()));
+            const uint32_t EID = node.as<uint32_t>();
+            fieldInfo->SetValue(object, EID == MAX_EID ? GameObject() : GameObject(EID));
         }
         else // Not any of the supported types
         {