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206 lines
10 KiB
ReStructuredText
206 lines
10 KiB
ReStructuredText
table
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=====
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a representation of a Lua (meta)table
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-------------------------------------
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.. code-block:: cpp
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template <bool global>
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class table_core;
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typedef table_core<false> table;
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typedef table_core<true> global_table;
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``sol::table`` is an extremely efficient manipulator of state that brings most of the magic of the Sol abstraction. Capable of doing multiple sets at once, multiple gets into a ``std::tuple``, being indexed into using ``[key]`` syntax and setting keys with a similar syntax (see: :doc:`here<proxy>`), ``sol::table`` is the corner of the interaction between Lua and C++.
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There are two kinds of tables: the global table and non-global tables: however, both have the exact same interface and all ``sol::global_table`` s are convertible to regular ``sol::table`` s.
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Tables are the core of Lua, and they are very much the core of Sol.
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members
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-------
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.. code-block:: cpp
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:caption: constructor: table
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table(lua_State* L, int index = -1);
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Takes a table from the Lua stack at the specified index and allows a person to use all of the abstractions therein.
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.. code-block:: cpp
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:caption: function: get / traversing get
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template<typename... Args, typename... Keys>
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decltype(auto) get(Keys&&... keys) const;
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template<typename T, typename... Keys>
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decltype(auto) traverse_get(Keys&&... keys) const;
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template<typename T, typename Key>
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decltype(auto) get_or(Key&& key, T&& otherwise) const;
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template<typename T, typename Key, typename D>
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decltype(auto) get_or(Key&& key, D&& otherwise) const;
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These functions retrieve items from the table. The first one (``get``) can pull out *multiple* values, 1 for each key value passed into the function. In the case of multiple return values, it is returned in a ``std::tuple<Args...>``. It is similar to doing ``return table["a"], table["b"], table["c"]``. Because it returns a ``std::tuple``, you can use ``std::tie``/``std::make_tuple`` on a multi-get to retrieve all of the necessary variables. The second one (``traverse_get``) pulls out a *single* value, using each successive key provided to do another lookup into the last. It is similar to doing ``x = table["a"]["b"]["c"][...]``.
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If the keys within nested queries try to traverse into a table that doesn't exist, the second lookup into the nil-returned variable and belong will cause a panic to be fired by the lua C API. If you need to check for keys, check with ``auto x = table.get<sol::optional<int>>( std::tie("a", "b", "c" ) );``, and then use the :doc:`optional<optional>` interface to check for errors. As a short-hand, easy method for returning a default if a value doesn't exist, you can use ``get_or`` instead.
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.. code-block:: cpp
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:caption: function: set / traversing set
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template<typename... Args>
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table& set(Args&&... args);
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template<typename... Args>
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table& traverse_set(Args&&... args);
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These functions set items into the table. The first one (``set``) can set *multiple* values, in the form ``key_a, value_a, key_b, value_b, ...``. It is similar to ``table[key_a] = value_a; table[key_b] = value_b, ...``. The second one (``traverse_set``) sets a *single* value, using all but the last argument as keys to do another lookup into the value retrieved prior to it. It is equivalent to ``table[key_a][key_b][...] = value;``.
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.. note::
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Value semantics are applied to all set operations. If you do not ``std::ref( obj )`` or specifically make a pointer with ``std::addressof( obj )`` or ``&obj``, it will copy / move. This is different from how :doc:`sol::function<function>` behaves with its call operator.
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.. code-block:: cpp
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:caption: function: add
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template<typename... Args>
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table& add(Args&&... args);
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This function appends a value to a table. The definition of appends here is only well-defined for a table which has a perfectly sequential (and integral) ordering of numeric keys with associated non-null values (the same requirement for the :ref:`size<size-function>` function). Otherwise, this falls to the implementation-defined behavior of your Lua VM, whereupon is may add keys into empty 'holes' in the array (e.g., the first empty non-sequential integer key it gets to from ``size``) or perhaps at the very "end" of the "array". Do yourself the favor of making sure your keys are sequential.
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Each argument is appended to the list one at a time.
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.. code-block:: cpp
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:caption: function: size
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:name: size-function
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std::size_t size() const;
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This function returns the size of a table. It is only well-defined in the case of a Lua table which has a perfectly sequential (and integral) ordering of numeric keys with associated non-null values.
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.. code-block:: cpp
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:caption: function: setting a usertype
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:name: new-usertype
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template<typename Class, typename... Args>
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table& new_usertype(const std::string& name, Args&&... args);
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template<typename Class, typename CTor0, typename... CTor, typename... Args>
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table& new_usertype(const std::string& name, Args&&... args);
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template<typename Class, typename... CArgs, typename... Args>
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table& new_usertype(const std::string& name, constructors<CArgs...> ctor, Args&&... args);
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This class of functions creates a new :doc:`usertype<usertype>` with the specified arguments, providing a few extra details for constructors. After creating a usertype with the specified argument, it passes it to :ref:`set_usertype<set_usertype>`.
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.. code-block:: cpp
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:caption: function: setting a simple usertype
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:name: new-simple-usertype
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template<typename Class, typename... Args>
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table& new_simple_usertype(const std::string& name, Args&&... args);
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template<typename Class, typename CTor0, typename... CTor, typename... Args>
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table& new_simple_usertype(const std::string& name, Args&&... args);
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template<typename Class, typename... CArgs, typename... Args>
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table& new_simple_usertype(const std::string& name, constructors<CArgs...> ctor, Args&&... args);
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This class of functions creates a new :doc:`simple usertype<simple_usertype>` with the specified arguments, providing a few extra details for constructors and passing the ``sol::simple`` tag as well. After creating a usertype with the specified argument, it passes it to :ref:`set_usertype<set_usertype>`.
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.. code-block:: cpp
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:caption: function: creating an enum
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:name: new-enum
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template<bool read_only = true, typename... Args>
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basic_table_core& new_enum(const std::string& name, Args&&... args);
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Use this function to create an enumeration type in Lua. By default, the enum will be made read-only, which creates a tiny performance hit to make the values stored in this table behave exactly like a read-only enumeration in C++. If you plan on changing the enum values in Lua, set the ``read_only`` template parameter in your ``new_enum`` call to false. The arguments are expected to come in ``key, value, key, value, ...`` list.
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.. _set_usertype:
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.. code-block:: cpp
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:caption: function: setting a pre-created usertype
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:name: set-usertype
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template<typename T>
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table& set_usertype(usertype<T>& user);
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template<typename Key, typename T>
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table& set_usertype(Key&& key, usertype<T>& user);
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Sets a previously created usertype with the specified ``key`` into the table. Note that if you do not specify a key, the implementation falls back to setting the usertype with a ``key`` of ``usertype_traits<T>::name``, which is an implementation-defined name that tends to be of the form ``{namespace_name 1}_[{namespace_name 2 ...}_{class name}``.
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.. code-block:: cpp
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:caption: function: begin / end for iteration
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:name: table-iterators
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table_iterator begin () const;
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table_iterator end() const;
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table_iterator cbegin() const;
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table_iterator cend() const;
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Provides `input iterators`_ for a table. This allows tables to work with single-pass, input-only algorithms (like ``std::for_each``).
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.. code-block:: cpp
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:caption: function: iteration with a function
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:name: table-for-each
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template <typename Fx>
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void for_each(Fx&& fx);
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A functional ``for_each`` loop that calls the desired function. The passed in function must take either ``sol::object key, sol::object value`` or take a ``std::pair<sol::object, sol::object> key_value_pair``. This version can be a bit safer as allows the implementation to definitively pop the key/value off the Lua stack after each call of the function.
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.. code-block:: cpp
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:caption: function: operator[] access
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template<typename T>
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proxy<table&, T> operator[](T&& key);
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template<typename T>
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proxy<const table&, T> operator[](T&& key) const;
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Generates a :doc:`proxy<proxy>` that is templated on the table type and the key type. Enables lookup of items and their implicit conversion to a desired type.
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.. code-block:: cpp
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:caption: function: set a function with the specified key into lua
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template<typename Key, typename Fx>
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state_view& set_function(Key&& key, Fx&& fx, [...]);
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Sets the desired function to the specified key value. Note that it also allows for passing a member function plus a member object or just a single member function: however, using a lambda is almost always better when you want to bind a member function + class instance to a single function call in Lua.
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.. code-block:: cpp
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:caption: function: create a table with defaults
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:name: table-create
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table create(int narr = 0, int nrec = 0);
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template <typename Key, typename Value, typename... Args>
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table create(int narr, int nrec, Key&& key, Value&& value, Args&&... args);
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static table create(lua_State* L, int narr = 0, int nrec = 0);
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template <typename Key, typename Value, typename... Args>
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static table create(lua_State* L, int narr, int nrec, Key&& key, Value&& value, Args&&... args);
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Creates a table, optionally with the specified values pre-set into the table. If ``narr`` or ``nrec`` are 0, then compile-time shenanigans are used to guess the amount of array entries (e.g., integer keys) and the amount of hashable entries (e.g., all other entries).
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.. code-block:: cpp
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:caption: function: create a table with compile-time defaults assumed
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:name: table-create-with
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template <typename... Args>
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table create_with(Args&&... args);
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template <typename... Args>
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static table create_with(lua_State* L, Args&&... args);
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Creates a table, optionally with the specified values pre-set into the table. It checks every 2nd argument (the keys) and generates hints for how many array or map-style entries will be placed into the table.
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.. code-block:: cpp
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:caption: function: create a named table with compile-time defaults assumed
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:name: table-create-named
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template <typename Name, typename... Args>
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table create_named(Name&& name, Args&&... args);
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Creates a table, optionally with the specified values pre-set into the table, and sets it as the key ``name`` in the table.
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.. _input iterators: http://en.cppreference.com/w/cpp/concept/InputIterator |