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IfDefinedPluginDescription
%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.
Related workSimilar extensions have been done before but are either only available as an integral part of TWiki-4.0 (see TWiki:TWiki04/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 conditon 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.Syntax RulesIFDEFINEDSyntax:
%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 emtpy 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:
IFDEFINEDTHEN, ELSIFDEFINED, ELSEDEFINED, FIDEFINEDSyntax:
%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 $nop string will be removed first.
Thereby nested TWikiML expressions can be prevented from being expanded in
advance.
IFACCESSSyntax:
%IFACCESS%
%IFACCESS{"<webtopic>"
[type="view|change"]
[user="<WikiName>"]
[then="<then-clause>"]
[else="<else-clause>"]
[glue="on|off"]}%
This checks the access permissions a user has on a given topic and then renders
the <then-clause> if access is granted and lt;else-clause> otherwise.
By default, the current user's view access will be checked on the current topic (%IFACCESS%).
The other parameters are:
IFEXISTSSyntax:
%IFEXISTS{"<webtopic>"
[then="<then-clause>"]
[else="<else-clause>"]
[glue="on|off"]}%
This tag checks if webtopic exists and expands then-clause or else-clause as needed.
A similar functionality is available using
%CALC{"$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.
Demo
Plugin Installation Instructions
Plugin Info
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