xo-reflect: + Object (cache TypeId for dispatching)

include/xo/reflect/Object.hpp

@@ -0,0 +1,44 @@
+** @file Object.hpp
+ *
+ *  Author: Roland Conybeare
+ **/
+
+#pragma once
+
+#include "xo/reflect/SelfTagging.hpp"
+//#include <cstdint>
+
+namespace xo {
+    namespace reflect {
+        /** @class Object
+         *
+         *  @brief A swiss-army-knife base class for runtime polymorphism.
+         *
+         *  Promote using this:
+         *  - for interpreter integration (see xo-expression / xo-jit)
+         *  - to allow reasonably efficient type dispatching -
+         *    don't need to pay for a function call to find out dispatching type.
+         **/
+        class Object : public reflect::SelfTagging {
+        public:
+            using TypeId = xo::reflect::TypeId;
+
+            Object(TypeId type_id) : type_id_{type_id} {}
+
+        private:
+            /** unique id number for this object's type
+             *
+             *  Caches the value of this->self_tp().td()->id()
+             *
+             *  Notes:
+             *  1. may want to record metatype also
+             *  2. a few builtin types have well-known type_ids.
+             *     see TypeDescrTable ctor in xo-reflect.
+             **/
+            TypeId type_id_;
+        };
+    } /*namespace obj*/
+} /*namespace xo*/
+
+
+/** end Object.hpp **/