struct IGameObjectSystem {
  struct SEntitySpawnParamsForGameObjectWithPreactivatedExtension {
    bool (* hookFunction)(IEntity * pEntity, IGameObject*, void * pUserData);
    void * pUserData;
  };
  const ExtensionID InvalidExtensionID = ~ExtensionID(0);
  const uint32 InvalidEventID = ~uint32(0);
};

IGameObjectSystem.h

struct SEntitySpawnParamsForGameObjectWithPreactivatedExtension {
  bool (* hookFunction)(IEntity * pEntity, IGameObject*, void * pUserData);
  void * pUserData;
};

IGameObjectSystem.h

If this is set as the user data for a GameObject with Preactivated Extension spawn, then it will be called back to provide additional initialization.

const uint32 InvalidEventID = ~uint32(0);

const ExtensionID InvalidExtensionID = ~ExtensionID(0);

virtual ~IGameObjectSystem();

virtual void AddSink(IGameObjectSystemSink * pSink) = 0;

virtual void BroadcastEvent(const SGameObjectEvent& evt) = 0;

virtual IGameObject * CreateGameObjectForEntity(EntityId entityId) = 0;

virtual void DefineProtocol(bool server, IProtocolBuilder * pBuilder) = 0;

virtual uint32 GetEventID(const char* name) = 0;

virtual const char* GetEventName(uint32 id) = 0;

virtual uint32 GetExtensionSerializationPriority(IGameObjectSystem::ExtensionID id) = 0;

virtual IGameObjectSystem::ExtensionID GetID(const char * name) = 0;

virtual const char * GetName(IGameObjectSystem::ExtensionID id) = 0;

virtual IGameObjectExtensionPtr Instantiate(IGameObjectSystem::ExtensionID id, IGameObject * pObject) = 0;

virtual void PostUpdate(float frameTime) = 0;

virtual void RegisterEvent(uint32 id, const char* name) = 0;

virtual void RegisterExtension(const char * name, IGameObjectExtensionCreatorBase * pCreator, IEntityClassRegistry::SEntityClassDesc * pEntityCls) = 0;

virtual void RemoveSink(IGameObjectSystemSink * pSink) = 0;

virtual void Reset() = 0;

virtual void SetPostUpdate(IGameObject * pGameObject, bool enable) = 0;

virtual void SetSpawnSerializer(TSerialize*) = 0;

typedef uint16 ExtensionID;

typedef IGameObjectExtension * (* GameObjectExtensionFactory)();