..  include:: /Includes.rst.txt
..  index:: TypoScript; Register usage
..  _using-setting-register:

========
Register
========

It is possible to store variable values into a memory stack which is called
"register".  The cObjects :ref:`LOAD_REGISTER <cobj-load-register>` and
:ref:`RESTORE_REGISTER <cobj-restore-register>` provide this storage functionality.
Some TYPO3 cObjects use internal registers. Esp.  the menus are built by
registers (e.g. count_HMENU, count_HMENU_MENUOBJ, count_menuItems).

..  _using-setting-register-defining-registers:

Defining registers
==================

Registers in TypoScript can be seen as stack array variables in programming
languages. Each register can store a complex TypoScript block. Use
:ref:`LOAD_REGISTER <cobj-load-register>` to put a variable to the stack, use
:ref:`RESTORE_REGISTER <cobj-restore-register>` to pull a variable from the stack
and curly braces around a variable name to read the current value of the
variable. You need a :ref:`data <stdwrap-data>` or a
:ref:`dataWrap <stdwrap-datawrap>` cObject. The registers cannot be read
on other places than inside of these cObjects.

..  _using-setting-register-example:

Example
=======

..  literalinclude:: _example2.typoscript
    :caption: EXT:my_sitepackage/Configuration/Sets/Main/setup.typoscript

This example shows a part of a TypoScript which builds a 2 column menu based on
a spacer page. A class is added to the ul tag depending on the value of the
register variable `ulClass`. The first pages will have the class `col-left` and
the pages following the spacer page will get the class `col-right`.

:typoscript:`{register:variablename}` returns the "current" value of the variable
`variablename`. A register stack can be like any TypoScript setup.

..  literalinclude:: _register.typoscript
    :caption: EXT:my_sitepackage/Configuration/Sets/Main/setup.typoscript

The "current" value is just an internal variable that can be used by functions
to pass a single value on to another function later in the TypoScript
processing. It is like "load accumulator" in the good old C64 days. Basically
you can use a "register" as you like. The TSref will tell if functions are
setting this value before calling some other object so that you know if it holds
any special information.