Register

It is possible to store variable values into a memory stack which is called “register”. The cObjects LOAD_REGISTER and RESTORE_REGISTER provide this storage functionality. Some TYPO3 cObjects use internal registers. Esp. the menus are built be registers (e.g. count_HMENU, count_HMENU_MENUOBJ, count_menuItems).

Defining registers

Registers in TypoScript can be seen as stack array variables in programming languages. Each register can store a complex TypoScript block. Use LOAD_REGISTER to put a variable to the stack, use 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 stdWrap.data or a stdWrap.dataWrap cObject. The registers cannot be read on other places than inside of these cObjects.

Example

10 = COA
10 {
    ### left menu table column
    10 = LOAD_REGISTER
    10 {
        ulClass = col-left
    }

    ### right menu table column
    20 = LOAD_REGISTER
    20 {
        ulClass = col-right
    }

    30 = HMENU
    30 {
        special = list
        special.value = 1
        1 = TMENU
        # ...
        3 = TMENU
        3 {
            stdWrap {
                preCObject = COA
                preCObject {
                    10 = RESTORE_REGISTER
                }
                dataWrap = <ul class="{register:ulClass}">|</ul>
            }
            wrap =
            SPC = 1
            SPC {
                allStdWrap {
                    replacement {
                        10 {
                            search = ---
                            replace =
                        }
                    }
                    dataWrap = </ul>|<ul class="{register:ulClass}">
                }
            }
        }
    }
}

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 .

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

10 = COA
10 {
  10 = LOAD_REGISTER
  10 {
      ulClass = col-left
      aClass = a-special
      colors {
          chief = red
          servant = white
      }
  }
}

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.