[TYPO3-core] RFC: Extend TypoScript values

[Michael Stucki]

Michael Stucki wrote:

> Finally committed! :-)
> I still have to document this in doc_core_ts, will do that next week.

This is my proposed documentation:

doc_core_ts, section "TypoScript Syntax":

=== cut ===

Operator is one of the characters =<>{( (Above: =). The significance of each
is described below.

=== cut ===

Just add one sentence:
There is one special operator ":=" that changes the value depending on a
predefined function.


... and some lines down, right after the description of the "=" operator:

=== cut ===

Value modifications: The ":="-operator

assigns a value to an object path by calling a predefined function and based
on the existing value of the current object path.
This is very useful for extending lists of page IDs etc. when a value should
be extended without redefining it completely again.

Rules:
- The portion after the ":="-operator and to the end of the line is split in
  two parts: A function and a value. The function is specified right next to
  the operator (trimmed) and holding the value in brackets (not trimmed).

- There are four predefined functions:
    addToList:
       Adds a comma-separated list of values to the end of a string value.
       There is no check for duplicate values, and the list is not sorted in
       any way.
    addString:
       Adds a string to the end of the existing value.
    removeFromList:
       Removes a comma-separated list of values from a comma-separated list.
    removeString:
       Removes a string from the existing value.

- There is a hook inside class.t3lib_tsparser.php which can be used to
  define more functions like this.

Example:
  myObject = TEXT
  myObject.value = 1,2,3
  myObject.value := addToList(4,5)
  myObject.value := removeFromList(2,1)

...results in the same like this:
  myObject = TEXT
  myObject.value = 3,4,5

=== cut ===

If nobody declines, I will commit this change tomorrow.

Regards, michael
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