IfDefinedPlugin
Render content conditionally
This plugin adds a couple of tags that allow to render content conditionally. There are two different ways to do that: either by using the inline
%IFDEFINED{"string" then="..." else="..."}% tag that returns the
then or
else argument depending on the
string being defined, that is non-empty. There are no other ways to decide the condition but rendering the
test string being a TWikiML expression, for example by embedding a
%CALC{}% expression. This simplifies this plugin alot and allows a rather flexible way to generate the condition.
The other way is to use blocks of content surrounded by expressions like this:
%IFDEFINEDTHEN{"test"}%
...
%ELSIFDEFINED{"test"}%
...
%ELSEDEFINED%
...
%FIDEFINED%
This way the conditioned content is not limited to fit into a the argument position of a
%IFDEFINED{...}% expression. Blocks can be nested and are evaluated starting from the outside, contrary to standard TWikiML being evaluated left-to-right-inside-out.
Similar extensions have been done before but are either only available as an integral part of TWiki-4.0 (see
TWiki:TWiki/IfStatements
) or unmaintained (see
TWiki:Plugins/ConditionalPlugin). Especially these two alternatives are rather similar as they defined the same tag (%IF). The main differences between those and this plugin here is that they have a more elaborated condition parser that allows to evaluate more complex boolean expressions. Some of the expressions in %IF of TWiki-4.0 are specific to that platform and make only sense there (context). The other difference is that the IFDEFINED tag family allows nested blocks of conditional content and %IF is an inline tag only.
The advantage of this plugin is that you get a simpler mechanism for checking the condition which is however more flexible as the string can be generated arbitrarily using TWikiML. Furthermore, and possibly more important, this plugin is backwards compatible and may be used on a TWiki/Beijing, TWiki/Cairo and TWiki/Dakar engine.
This plugin has been externalized from the
TWiki:Plugins/NatSkinPlugin.
IFDEFINED
Syntax:
%IFDEFINED{"test"
[action="view,edit,preview,..."]?
[as="..."]
then="..."
else="..."
glue="on,off"}%
returns the "then or "else" content depending on the "test" expression expanding to the empty string or matching the string given in "as". Optionally the current topic action is checked to match the one given in "action". Normally, all surrounding whitespaces are removed, that is the resulting content is glued together in a way. You may switch that off by setting "glue" to "off" thus preventing all whitespace as it is.
The "then" and "else" strings may contain the following pseudo-variables:
-
$n: substituted with a newline character (\n)
-
$percnt: substituted with a percent character (%)
-
$dollar: substituted with a dollar character ($)
-
$test or $variable: substituted with the "test" string
-
$value: substituted with the "as" string
IFDEFINEDTHEN, ELSIFDEFINED, ELSEDEFINED, FIDEFINED
Syntax:
%IFDEFINEDTHEN{"test" [action="view,edit,preview,..."]?}%
<then content>
[%ELSIFDEFINED{...}%
<elsif content>]*
[%ELSEDEFINED%
<else content>]?
%FIDEFINED%
This is the multi-line version of
IFSDEFINED. IFDEFINEDTHEN expressions can be nested safely. Within a single IFDEFINEDTHEN the ELSIFDEFINED parts can be repeated arbitrarily. Before rendering the
<then|elsif|else condition> any
$nop string will be removed first. Thereby nested TWikiML expressions can be prevented from being expanded in advance.
IFACCESS
Syntax:
%IFACCESS%
%IFACCESS{"<webtopic>"
[type="view|change"]
[user="<WikiName>"]
[then="<then-clause>"]
[else="<else-clause>"]
[glue="on|off"]}%
This checks the access permissions a user has on a given topic and then renders the
<then-clause> if access is granted and
lt;else-clause> otherwise. By default, the current user's view access will be checked on the current topic (
%IFACCESS%). The other parameters are:
-
<webtopic>: the name of the topic to be checked, defaults to current
-
user="<WikiName>": the name of the user to be checked, defaults to the current user
-
type="view|change": the type of access to be checked, either view access or change/edit access, defaults to "view"
-
then="<then-clause>": the string to be returned on granted access, defaults to "1"
-
else="<else-clause>": the string to be returned if no access is granted, defaults to "0"
-
glue="on|off": apply glue around the IFACCESS tag or not, defaults to "on"
IFEXISTS
Syntax:
%IFEXISTS{"<webtopic>"
[then="<then-clause>"]
[else="<else-clause>"]
[glue="on|off"]}%
This tag checks if
webtopic exists and expands
then-clause or
else-clause as needed. A similar functionality is available using
%CALC{"$IF($EXIST(<webtopic>,<then-clause>),<else-clause>)"}% of the
SpreadSheetPlugin. This is still preferable if you need more computation based on CALC in the then/else branches. The IFEXISTS version however is more lightweigted, comes with a much simpler syntax and allows more complex TWikiMarkup in the then/else branches.
- Download the ZIP file (see below)
- Unzip it in your twiki installation directory. Content:
|
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| File: |
Description: |
data/TWiki/IfDefinedPlugin.txt |
Plugin topic |
lib/TWiki/Plugins/IfDefinedPlugin.pm |
Plugin Perl module |
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- Visit
configure in your TWiki installation, and enable the plugin in the {Plugins} section.
Related Topics: VarIF,
IfStatements,
SpreadSheetPlugin,
TWikiPlugins,
DeveloperDocumentationCategory,
AdminDocumentationCategory,
TWikiPreferences