general-purpose safety reference to an existing object

class object : reference;

object’s goal is to allow someone to pass around the most generic form of a reference to something in Lua (or propogate a nil). It is the logical extension of sol::reference, and is used in sol::table’s iterators.


overloaded constructor: object
template <typename T>
object(lua_State* L, int index = -1);
template <typename T, typename... Args>
object(lua_State* L, in_place_t, T&& arg, Args&&... args);
template <typename T, typename... Args>
object(lua_State* L, in_place_type_t<T>, Args&&... args);

There are 4 kinds of constructors here. One allows construction of an object from other reference types such as sol::table and sol::stack_reference. The second creates an object which references the specific element at the given index in the specified lua_State*. The more advanced in_place... constructors create a single object by pushing the specified type T onto the stack and then setting it as the object. It gets popped from the stack afterwards (unless this is an instance of sol::stack_object, in which case it is left on the stack). An example of using this and sol::make_object can be found in the any_return example.

function: type conversion
template<typename T>
decltype(auto) as() const;

Performs a cast of the item this reference refers to into the type T and returns it. It obeys the same rules as sol::stack::get<T>.

function: type check
template<typename T>
bool is() const;

Performs a type check using the sol::stack::check api, after checking if the internally stored reference is valid.


functions: nil comparators
bool operator==(const object& lhs, const nil_t&);
bool operator==(const nil_t&, const object& rhs);
bool operator!=(const object& lhs, const nil_t&);
bool operator!=(const nil_t&, const object& rhs);

These allow a person to compare an sol::object against nil, which essentially checks if an object references a non-nil value, like so:

if (myobj == sol::lua_nil) {
        // doesn't have anything...