Design Optimization

Using the (:if:) Directive

The (:if:) directive allows portions of a page to be included or excluded from rendering. The generic forms of the (:if:) directive are

where "cond" names a condition to be tested, and "param" is a parameter or other argument to the condition.

Note that (:if:) without parameters and (:ifend:) are identical. Also note that (:if cond:) automatically closes a previous conditional. For nested multiple levels, see Nested conditionals.

Built-in Conditions

The built-in conditions include:

The name and group conditionals will work even for an included page, as the "name" and "group" conditionals always check the currently displayed page, as opposed to the page that the markup appears in.

Note: Although there is no built-in conditional markup to test ?action=, you can use (:if equal {$Action} ACTION:) to test what the current action being requested is.

Concatenated conditions

In some cases where built in conditions have a parameter the parameters may be concatenated using a comma, viz:

• (:if page Name1,Name2,-Name3:)
• (:if group -Group1,Group,Group3:)

Negated Conditions

Negated forms of conditions also work:

Nesting Conditions

Note that (:if cond:) automatically closes a previous conditional. Thus, the following two examples have identical meaning:

• (:if cond1:) cond1 is true (:if cond2:) cond2 is true (:ifend:)
• (:if cond1:) cond1 is true (:ifend:)(:if cond2:) cond2 is true (:ifend:)

Conditions can be nested from 2.2.beta 66. To have nested conditionals you need to number the if, and the matching else/ifend:

(:if cond1:)
  cond1 is true
  (:if2 cond2:)
     cond1 and cond2 are true
  (:else2:)
     cond1 is true, cond2 is not
  (:if2end:)
(:else:)
  cond1 is false, cond2 testing was ignored
(:ifend:)

Spaces were added for better readability.

Using wildcard placeholders

The character * can be used as a wildcard to represent any character, zero, one, or multiple times.
The character ? can be used as a wildcard to represent any character exactly once.
Wildcard characters (* and ?) can be used with the name and group conditional markups, thus:

Using page text variables, page variables and markup expressions

Page text variables (PTVs), page variables (PVs) and markup expressions can be used in conditional markup. They will be assigned/evaluated before the condition(s).

Combining conditions

Conditions (as previously defined) may be combined into more complex conditional expressions using one of these three equivalent forms:

(:if expr EXPRESSION :)
(:if [ EXPRESSION ] :)
(:if ( EXPRESSION ) :)

Conditions are combined into expressions with boolean operators and brackets. In the next table, A and B are either regular conditions or (round-)bracketed sub-expressions of regular conditions:

Example

(:if [ name SomePage and group SomeGroup ]:)    equivalent to (:if name SomeGroup.SomePage:)

Important Notes:

• Spaces are required around operators and brackets.
• No specific feedback is given for syntax errors or unbalanced brackets.
• Use round brackets (not square) for nested expressions.

Thus, the following is a valid way of building an expression that shows the following contents only when the user is either the administrator, or is logged in and the time is later than the given date:

Nesting with square brackets will silently fail to work as expected:

A common use of these complex tests are for expressions like:

which provides a logout link only when the browser has admin, attr, or edit permissions.

admins (advanced)

Creating new conditions

See Cookbook:ConditionalMarkupSamples.

See also special references for the use of {*$Variables}.