IF Statements
The
%IF%
construct gives TWiki the power to include content in topics based on the value of simple expressions.
%IF{"CONDITION" then="THEN" else="ELSE"}%
In the example above, if CONDITION evaluates to TRUE, then THEN will be included in the topic; otherwise ELSE will be included.
Note that because of the way TWiki evaluates, then whatever is in the THEN and ELSE parameters will already have been expanded by the time the condition is actually evaluated. The standard
FormatTokens can be used in the THEN and ELSE parameters when you need to delay evaluation of (for example) a TWiki variable.
The basic syntax of a condition is the same as
the syntax used for queries, with operators
=
,
!=
,
~
,
<
,
>
,
<=
,
>=
,
NOT
,
AND
,
OR
,
()
, and functions
lc()
,
uc()
,
d2n()
. In addition, the following special operators are supported:
context |
True if the current context is set (see below) |
allows |
'X' allows 'Y' is true if web/topic 'X' exists and allows access mode 'Y' for the current user. Web access rights are only checked if there is no topic called 'X'. |
istopic |
istopic 'X' is true if topic 'X' exists |
isweb |
isweb 'X' is true if web 'X' exists |
ingroup |
'X' ingroup 'Y' is true if user 'X' is in group 'Y'. 'X' can be a login name or a wikiname. |
defined |
True if a preference variable or url parameter of this name is defined. |
isempty |
True if a preference variable, url parameter or session variable of this name has an empty value. It is equivalent to the expression (defined(x) || $x='') |
$ |
expands a URL parameter or TWikiVariable name. 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 "). |
{X} |
expands to the value of the configuration variable {X} - for example, {ScriptUrlPath} |
Examples:
1. TWiki variable defined or not
%IF{"defined 'WIKINAME'" then="WIKINAME is defined" else="WIKINAME is not defined"}%
2. Compare TWiki variable
You are %IF{ "$ WIKINAME='TWikiGuest' and not defined 'OPEN_DAY'" then="not" }% allowed to
%IF{ "context view" then="view" else="edit"}% this TWiki today.
3. URL parameter
%IF{ "defined 'search'" then="Search: $percntURLPARAM{search}$percnt" else="No search passed in"}%
4. Range test on URL parameter
url param t is %IF{ "0 < $ t and $ t < 1000" then="in" else="out of"}% range.
5. Text comparison of URL parameter
%IF{ "$'URLPARAM{scope}'='text'" then="Plain text search" }%
6. Configuration item set or not
%IF{ "{AntiSpam}{HideUserDetails}" then="User details are hidden" }%
7. Plugin enabled test
TablePlugin is %IF{ "context TablePluginEnabled" then="enabled" else="disabled" }%.
expands to:
TablePlugin is enabled.
8. Check access permissions
You %IF{"'%TOPIC%' allows 'change'" then="can" else="cannot"}% change this topic.
You %IF{"'Sandbox.TestTopic' allows 'change'" then="can" else="cannot"}% change Sandbox.TestTopic.
You %IF{"'Sandbox' allows 'change'" then="can" else="cannot"}% change Sandbox web
expands to:
You cannot change this topic.
You can change
TestTopic.
You can change Sandbox web
9. Check topic existance
Topic Sandbox.TestTopic %IF{"istopic 'Sandbox.TestTopic'" then="exists" else="does not exist"}%
Web Sandbox.TestTopic %IF{"isweb 'Sandbox'" then="exists" else="does not exist"}%
expands to:
Topic
TestTopic exists
Web
TestTopic exists
10. Group membership
You %IF{"'%USERNAME%' ingroup 'TWikiAdminGroup'" then="are an admin" else="are a normal user"}%
expands to:
You are a normal user
11. Hide section of text conditionally using CSS visibility
<div style="visibility: %IF{"'%USERNAME%' ingroup 'TWikiAdminGroup'" then="visible" else="hidden"}%">
* Conditional text enclosed in div tags here...
* ...can be as long as needed
</div>
Above text is only shown to users who are in the TWikiAdminGroup.
Configuration items are defined in
configure. You cannot see the value of a configuration item, you can only see if the item is set or not.
Context identifiers are used in TWiki to label various stages of the rendering process. They are especially useful for
skin authors to find out where they are in the rendering process. The following context identifiers are available:
id |
context |
i18n_enabled |
when user interface I18N support is enabled (i.e., user can choose the language for UI) |
header_text |
when the header text is being processed in a view (useful in plugin handlers) |
footer_text |
when the footer text is being processed in a view (useful in plugin handlers) |
body_text |
when the body text is being processed in a view (useful in plugin handlers) |
command_line |
the running script was run from the command line, and not from CGI |
passwords_modifyable |
set if the password manager support changing the password / email |
absolute_urls |
Set if absolute URLs are required |
registration_enabled |
set if {Register}{EnableNewUserRegistration} is on, and registrationis supported |
registration_supported |
registration is supported by the current UserMapper |
textareas_hijacked |
provided for use by editors that highjack textareas, and want to signal this fact. This is used by skins, for example, so they can suppress extra controls when textareas have been hijacked. |
viewfile |
in viewfile script (see TWikiScripts) |
view |
in view script (see TWikiScripts) |
upload |
in upload script (see TWikiScripts) |
statistics |
in statistics script (see TWikiScripts) |
search |
in search script (see TWikiScripts) |
save |
in save script (see TWikiScripts) |
rest |
in rest script (see TWikiScripts) |
resetpasswd |
in resetpasswd script (see TWikiScripts) |
rename |
in rename script (see TWikiScripts) |
register |
in register script (see TWikiScripts) |
diff |
in rdiff script (see TWikiScripts) |
preview |
in preview script (see TWikiScripts) |
oops |
in oops script (see TWikiScripts) |
manage |
in manage script (see TWikiScripts) |
login & logon |
in login / logon script (see TWikiScripts) |
edit |
in edit script (see TWikiScripts) |
changes |
in changes script (see TWikiScripts) |
attach |
in attach script (see TWikiScripts) |
rss |
if this is an RSS skin rendering |
mirror |
if this is a mirror |
new_topic |
if the topic doesn't already exist |
inactive |
if active links such as 'edit' and 'attach' should be disabled |
can_login |
current environment supports login |
authenticated |
a user is authenticated |
In addition there is a context identifier for each enabled plugin; for example, if
GallousBreeksPlugin
is installed
and enabled, then the context ID
GallousBreeksPluginEnabled
will be set. Other extensions may set additional context identifiers.
The
%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.
Note also that while the
query syntax can be used to access form fields, there are some contexts in which an IF statement may be used where there is no topic context, or the topic context is not what you expected.
Related Topics: QuerySearch,
VarIF,
VarGET,
VarSET,
VarSEARCH,
FormattedSearch,
FormatTokens,
SpreadSheetPlugin,
TWikiScripts
--
Contributors: TWiki:Main.ArthurClemens,
TWiki:Main.CrawfordCurrie,
TWiki:Main.PeterThoeny,
TWiki:Main.SopanShewale,
TWiki:Main.SvenDowideit,
TWiki:Main.WillNorris - 2011-04-04