iw7-mod/deps/sol2/documentation/source/api/object.rst

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2024-08-13 05:15:34 -04:00
object
======
*general-purpose safety reference to an existing object*
.. code-block:: cpp
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 :doc:`sol::reference<reference>`, and is used in :ref:`sol::table's iterators<table-iterators>`.
members
-------
.. code-block:: cpp
:caption: overloaded constructor: object
:name: overloaded-object-constructor
template <typename T>
object(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 :doc:`sol::table<table>` and :doc:`sol::stack_reference<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 :doc:`sol::make_object<make_reference>` can be found in the `any_return example`_.
.. code-block:: cpp
:caption: 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 :ref:`sol::stack::get\<T><stack-get>`.
.. code-block:: cpp
:caption: function: type check
template<typename T>
bool is() const;
Performs a type check using the :ref:`sol::stack::check<stack-check>` api, after checking if the internally stored reference is valid.
non-members
-----------
.. code-block:: cpp
:caption: 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 :ref:`nil<nil>`, which essentially checks if an object references a non-nil value, like so:
.. code-block:: cpp
if (myobj == sol::lua_nil) {
// doesn't have anything...
}
.. _any_return example: https://github.com/ThePhD/sol2/blob/develop/examples/source/any_return.cpp