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diff --git a/3rdparty/sol2/docs/source/api/proxy.rst b/3rdparty/sol2/docs/source/api/proxy.rst new file mode 100644 index 00000000000..897dbbaf7dd --- /dev/null +++ b/3rdparty/sol2/docs/source/api/proxy.rst @@ -0,0 +1,201 @@ +proxy, (protected\_)function_result - proxy_base derivatives +============================================================ +``table[x]`` and ``function(...)`` conversion struct +---------------------------------------------------- + +.. code-block:: c++ + + template <typename Recurring> + struct proxy_base; + + template <typename Table, typename Key> + struct proxy : proxy_base<...>; + + struct stack_proxy: proxy_base<...>; + + struct function_result : proxy_base<...>; + + struct protected_function_result: proxy_base<...>; + + +These classes provide implicit assignment operator ``operator=`` (for ``set``) and an implicit conversion operator ``operator T`` (for ``get``) to support items retrieved from the underlying Lua implementation, specifically :doc:`sol::table<table>` and the results of function calls on :doc:`sol::function<function>` and :doc:`sol::protected_function<protected_function>`. + +.. _proxy: + +proxy +----- + +``proxy`` is returned by lookups into :doc:`sol::table<table>` and table-like entities. Because it is templated on key and table type, it would be hard to spell: you can capture it using the word ``auto`` if you feel like you need to carry it around for some reason before using it. ``proxy`` evaluates its arguments lazily, when you finally call ``get`` or ``set`` on it. Here are some examples given the following lua script. + +.. code-block:: lua + :linenos: + :caption: lua nested table script + + bark = { + woof = { + [2] = "arf!" + } + } + + +After loading that file in or putting it in a string and reading the string directly in lua (see :doc:`state`), you can start kicking around with it in C++ like so: + +.. code-block:: c++ + :linenos: + + sol::state lua; + + // produces proxy, implicitly converts to std::string, quietly destroys proxy + std::string x = lua["bark"]["woof"][2]; + + +``proxy`` lazy evaluation: + +.. code-block:: c++ + :linenos: + :caption: multi-get + + auto x = lua["bark"]; + auto y = x["woof"]; + auto z = x[2]; + // retrivies value inside of lua table above + std::string value = z; // "arf!" + // Can change the value later... + z = 20; + // Yay, lazy-evaluation! + int changed_value = z; // now it's 20! + + +We don't recommend the above to be used across classes or between function: it's more of something you can do to save a reference to a value you like, call a script or run a lua function, and then get it afterwards. You can also set functions (and function objects :ref:`*<note 1>`) this way, and retrieve them as well. + +.. code-block:: c++ + :linenos: + + lua["bark_value"] = 24; + lua["chase_tail"] = floof::chase_tail; // chase_tail is a free function + + +members +------- + +.. code-block:: c++ + :caption: functions: [overloaded] implicit conversion get + :name: implicit-get + + requires( sol::is_primitive_type<T>::value == true ) + template <typename T> + operator T() const; + + requires( sol::is_primitive_type<T>::value == false ) + template <typename T> + operator T&() const; + +Gets the value associated with the keys the proxy was generated and convers it to the type ``T``. Note that this function will always return ``T&``, a non-const reference, to types which are not based on :doc:`sol::reference<reference>` and not a :doc:`primitive lua type<types>` + +.. code-block:: c++ + :caption: function: get a value + :name: regular-get + + template <typename T> + decltype(auto) get( ) const; + +Gets the value associated with the keys and converts it to the type ``T``. + +.. code-block:: c++ + :caption: function: optionally get a value + :name: regular-get-or + + template <typename T, typename Otherwise> + optional<T> get_or( Otherwise&& otherise ) const; + +Gets the value associated with the keys and converts it to the type ``T``. If it is not of the proper type, it will return a ``sol::nullopt`` instead. + +``operator[]`` proxy-only members +--------------------------------- + +.. code-block:: c++ + :caption: function: valid + :name: proxy-valid + + bool valid () const; + +Returns whether this proxy actually refers to a valid object. It uses :ref:`sol::stack::probe_get_field<stack-probe-get-field>` to determine whether or not its valid. + +.. code-block:: c++ + :caption: functions: [overloaded] implicit set + :name: implicit-set + + requires( sol::detail::Function<Fx> == false ) + template <typename T> + proxy& operator=( T&& value ); + + requires( sol::detail::Function<Fx> == true ) + template <typename Fx> + proxy& operator=( Fx&& function ); + +Sets the value associated with the keys the proxy was generated with to ``value``. If this is a function, calls ``set_function``. If it is not, just calls ``set``. Does not exist on :ref:`function_result<function-result>` or :ref:`protected_function_result<protected-function-result>`. See :ref:`note<note 1>` for caveats. + +.. code-block:: c++ + :caption: function: set a callable + :name: regular-set-function + + template <typename Fx> + proxy& set_function( Fx&& fx ); + +Sets the value associated with the keys the proxy was generated with to a function ``fx``. Does not exist on :ref:`function_result<function-result>` or :ref:`protected_function_result<protected-function-result>`. + + +.. code-block:: c++ + :caption: function: set a value + :name: regular-set + + template <typename T> + proxy& set( T&& value ); + +Sets the value associated with the keys the proxy was generated with to ``value``. Does not exist on :ref:`function_result<function-result>` or :ref:`protected_function_result<protected-function-result>`. + +stack_proxy +----------- + +``sol::stack_proxy`` is what gets returned by :doc:`sol::variadic_args<variadic_args>` and other parts of the framework. It is similar to proxy, but is meant to alias a stack index and not a named variable. + +.. _function-result: + +function_result +--------------- + +``function_result`` is a temporary-only, intermediate-only implicit conversion worker for when :doc:`function<function>` is called. It is *NOT* meant to be stored or captured with ``auto``. It provides fast access to the desired underlying value. It does not implement ``set`` / ``set_function`` / templated ``operator=``, as is present on :ref:`proxy<proxy>`. + + +.. _protected-function-result: + +protected_function_result +------------------------- + +``protected_function_result`` is a nicer version of ``function_result`` that can be used to detect errors. Its gives safe access to the desired underlying value. It does not implement ``set`` / ``set_function`` / templated ``operator=`` as is present on :ref:`proxy<proxy>`. + + +.. _note 1: + +on function objects and proxies +------------------------------- + +Consider the following: + +.. code-block:: cpp + :linenos: + :caption: Note 1 Case + + struct doge { + int bark; + + void operator()() { + bark += 1; + } + }; + + sol::state lua; + lua["object"] = doge{}; // bind constructed doge to "object" + // but it binds as a function + +When you use the ``lua["object"] = doge{};`` from above, keep in mind that Sol detects if this is a function *callable with any kind of arguments*. Since ``doge`` has overriden ``return_type operator()( argument_types... )`` on itself, it results in satisfying the ``requires`` constraint from above. This means that if you have a user-defined type you want to bind as a :doc:`userdata with usertype semantics<usertype>` with this syntax, it might get bound as a function and not as a user-defined type (d'oh!). use ``lua["object"].set(doge)`` directly to avoid this, or ``lua["object"].set_function(doge{})`` to perform this explicitly.
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