82 lines
4.5 KiB
Plaintext
82 lines
4.5 KiB
Plaintext
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%META:TOPICINFO{author="TWikiContributor" date="1111929255" format="1.0" version="4"}%
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---+ =IF= Statements
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The =%<nop>IF%= construct gives TWiki the power to include content in topics based on the value of simple expressions.
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=%<nop>IF{"CONDITION" then="THEN" else="ELSE"}%=
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In the example above, if CONDITION evaluates to TRUE, then THEN will be included in the topic; otherwise ELSE will be included.
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What can be included in the THEN and ELSE parameters is obviously limited by standard TWiki syntax for parameters.
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The basic syntax of a condition is as follows:
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<verbatim>
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expr ::= '(' expr ')' ;
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expr ::= andexpr | andexpr 'or' expr ;
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andexpr ::= notexpr | notexpr 'and' andexpr ;
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notexpr ::= basexpr | 'not' baseexpr ;
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basexpr ::= atom | uop atom | atom bop basexpr ;
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uop ::= 'context' | 'defined' | '$' ;
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bop ::= '=' | '!=' | '>' | '<' | '>=' | '<=' ;
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atom ::= context identifier, TWiki variable name, single-quoted string, or configuration item
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</verbatim>
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| *Operators* ||
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| and | True if both sides are true |
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| or | True if one or other side is true |
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| not | negate the following expression |
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| <nop>=, !<nop>= | String comparison |
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| <, >, <=, >= | Number comparison (there is no explicit numeric =) |
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| context | True if the current context is set (see below) |
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| defined | True if a preference variable or url parameter of this name is defined. |
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| $ | expands a URL parameter or [[TWikiVariables][TWikiVariable]]. Plugin handlers *are not called*. Built-in variables and user-defined preferences are supported. You can pass a limited subset of parameters to TWiki variables by enclosing the variable name in single quotes; for example, =$ 'VARIABLE{value}'=. The ='VARIABLE{value}'= string may *not* contain quotes (' or "). |
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examples:
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<verbatim>
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TWiki variable defined or not
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%IF{"defined WIKINAME" then="WIKINAME is defined" else="WIKINAME is not defined"}%
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You are %IF{ "$ WIKINAME='TWikiGuest' and not defined OPEN_DAY" then="not" }% allowed to
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%IF{ "context view" then="view" else="edit"}% this TWiki today.
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URL parameter
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%IF{ "defined search" then="Search: %URLPARAM{search}%" else="No search passed in"}%
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Configuration item set or not
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%IF{ "{AntiSpam}{HideUserDetails}" then="User details are hidden" }%
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url param t is %IF{ "0 < $ t and $ t < 1000" then="in" else="out of"}% range.
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Text comparison
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%IF{ "$'URLPARAM{scope}'='text'" then="Plain text search" }%
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</verbatim>
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*Configuration items* are defined in [[%SCRIPTURLPATH{"configure"}%][configure]]. You cannot see the value of a configuration item, you can only see if the item is set or not.
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*Context identifiers* are used in TWiki to label various stages of the rendering process. They are especially useful for [[TWikiSkins][skin]] authors to find out where they are in the rendering process. The following context identifiers are available:
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| *id* | *context* |
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| absolute_urls | Set if absolute URLs are required |
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| authenticated | a user is authenticated |
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| body_text | when the body text is being processed in a view (useful in plugin handlers) |
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| can_login | current environment supports login |
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| changes | in changes script (see TWikiScripts) |
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| command_line | the running script was run from the command line, and not from CGI |
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| diff | in rdiff script (see TWikiScripts) |
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| edit | in edit script (see TWikiScripts) |
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| footer_text | when the footer text is being processed in a view (useful in plugin handlers) |
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| header_text | when the header text is being processed in a view (useful in plugin handlers) |
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| i18n_enabled | when user interface I18N support is enabled (i.e., user can choose the language for UI) |
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| inactive | if active links such as 'edit' and 'attach' should be disabled |
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| mirror | if this is a mirror |
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| new_topic | if the topic doesn't already exist |
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| oops | in oops script (see TWikiScripts) |
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| preview | in preview script (see TWikiScripts) |
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| rss | if this is an RSS skin rendering |
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| save | in save script (see TWikiScripts) |
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| search | in search script (see TWikiScripts) |
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| view | in view script (see TWikiScripts) |
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| rest | in rest script (see TWikiScripts) |
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In addition there is a context identifier for each enabled plugin; for example, if =Gallous<nop>BreeksPlugin= is installed *and enabled*, then the context ID =Gallous<nop>BreeksPluginEnabled= will be set. Other extensions may set additional context identifiers.
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The =%<nop>IF%= statement is deliberately kept simple. In particular, note that there is no way to conditionally execute a Set statement. If you need more sophisticated control over formatting, then consider using the SpreadSheetPlugin.
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