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You are here: System » SetVariablePlugin


Flexible handling of topic variables

The main purpose of this plugin is to allow to set topic variables when saving a topic. Url parameters posted to save will be parsed and stored into the current topic.

Parameters must have the form:


Which means:

  • Local+<key>=<value> will create a local topic variable called key with value =value
  • Set+<key>=<value> will create a normal topic variable called key with value =value (note if stored in a user topic these take effect on all of the site for this user; see the Foswiki documentation for a more in depth explanation)
  • Unset+<key>=<value> will remove a topic variable called key from the topic
  • Default+<key>=<value> defines the default values for a variable key; if key is set to this value, it will actually be remove from the topic as it is being set to a default value

In addition to setting topic variables via url parameters of a save action, this plugin provides means to read and write topic variables in WikiApplications. Among other use cases these can be used to create appropriate html forms for topic variables as far as the function is not provided by standard TML part of the Foswiki core.

When SETVAR and UNSERVAR are parsed during the discourse of creating the current page they don't set the topic variable immediately. Instead they create a definition rule. All definition rules are collected and applied to the topic at the end of the parsing process. That way multiple SETVAR and UNSERVAR - that potentially contradict each other - stack up. The last rule on the stack wins and decides wether a variable is set or deleted. This allows to create more extensive rule sets.

Syntax Rules



This sets topic variable key to value value if the formfield fieldname of the current topic matches pattern. This allows to set topic variables based on the value of a formfield value. For example, that's useful to create access control settings automatically.



This unsets topic variable key when formfield formfield fieldname of the current topic matches pattern



This displays a variable key as stored in topic web.topic and formats it using the given format. It's type can be any of the known Foswiki meta data specifies like PREFERENCE, FIELD, TOPICINFO etc. When no definition of key was found the default value is returned. Instead of extracting a variable from web.topic it can also be extracted from a specific scope.

Normally all scopes are layered above each other and only the value defined in the scope with highest precedence is returned. So when ever a variable is set in a topic, it will potentially override its definition on web level or user level. You may use the scope parameter to bypass this logic and extract a specific value from the given scope specifier.

Multiple variables can be returned by one call if you use a pattern instead of a key holding a regular expression. GETVAR will return all variable values of the given type where the pattern matches on the variable name. The list of variables will be displayed using format preceded by header and appended by footer. The header and footer will be omitted when no matching variable was found.

The format string may contain the standard escape parameters

  • $percnt,
  • $dollar,
  • $nop and
  • $n as well as
  • $value - the value of the current variable
  • $name - the name of the current variable
  • $title - the title and the
  • $type - which is Set, Local, =Web or =Session depending on the type and scope of the variable


Display a table of all definition rules as far as collected by SETVAR and UNSERVAR.

Installation Instructions

You do not need to install anything in the browser to use this extension. The following instructions are for the administrator who installs the extension on the server.

Open configure, and open the "Extensions" section. Use "Find More Extensions" to get a list of available extensions. Select "Install".

If you have any problems, or if the extension isn't available in configure, then you can still install manually from the command-line. See http://foswiki.org/Support/ManuallyInstallingExtensions for more help.

Plugin Info

Plugin Author: Foswiki:Main.MichaelDaum
Copyright: © 2007-2009 Michael Daum http://michaeldaumconsulting.com
License: GPL (GNU General Public License)
Plugin Version: 1.00
Change History:  
23 Jun 2009: initial release
Dependencies: None
Plugin Home: Foswiki:Extensions/SetVariablePlugin
Feedback: Foswiki:Extensions/SetVariablePluginDev
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