#define SOL_ALL_SAFETIES_ON 1 #include #include #include struct Shape { virtual ~Shape() = default; }; struct Box : Shape { }; SOL_BASE_CLASSES(Box, Shape); SOL_DERIVED_CLASSES(Shape, Box); int main() { sol::state lua; lua.open_libraries(sol::lib::base); lua.new_usertype("Shape", sol::no_constructor); lua.new_usertype("Box", sol::factories([&]() { auto b = std::make_shared(); std::cout << "create Box@" << std::hex << b.get() << '\n'; return b; })); lua.set_function( "inspect_shape_table", [](const sol::table& args) { std::shared_ptr defbox = nullptr; // check if there's a field with the name "shape" auto s = args.get< sol::optional>>( "shape"); std::cout << "has : " << std::boolalpha << s.has_value() << '\n'; // get the field named "shape" or use the default // value std::cout << "get_or: " << std::hex << args.get_or>( "shape", defbox) .get() << '\n'; // this works but I can't test for existence // beforehand... std::cout << "get : " << std::hex << args.get>("shape") .get() << '\n'; }); sol::protected_function_result result = lua.safe_script( "inspect_shape_table({shape=Box.new()})"); SOL_ASSERT(result.valid()); return 0; }