69 lines
2.6 KiB
ReStructuredText
69 lines
2.6 KiB
ReStructuredText
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object
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======
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*general-purpose safety reference to an existing object*
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.. code-block:: cpp
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class object : reference;
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``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>`.
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members
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-------
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.. code-block:: cpp
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:caption: overloaded constructor: object
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:name: overloaded-object-constructor
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template <typename T>
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object(T&&);
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object(lua_State* L, int index = -1);
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template <typename T, typename... Args>
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object(lua_State* L, in_place_t, T&& arg, Args&&... args);
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template <typename T, typename... Args>
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object(lua_State* L, in_place_type_t<T>, Args&&... args);
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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`_.
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.. code-block:: cpp
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:caption: function: type conversion
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template<typename T>
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decltype(auto) as() const;
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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>`.
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.. code-block:: cpp
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:caption: function: type check
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template<typename T>
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bool is() const;
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Performs a type check using the :ref:`sol::stack::check<stack-check>` api, after checking if the internally stored reference is valid.
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non-members
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-----------
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.. code-block:: cpp
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:caption: functions: nil comparators
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bool operator==(const object& lhs, const nil_t&);
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bool operator==(const nil_t&, const object& rhs);
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bool operator!=(const object& lhs, const nil_t&);
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bool operator!=(const nil_t&, const object& rhs);
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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:
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.. code-block:: cpp
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if (myobj == sol::lua_nil) {
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// doesn't have anything...
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}
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.. _any_return example: https://github.com/ThePhD/sol2/blob/develop/examples/source/any_return.cpp
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