Help:Parser functions in templates

2009-07-12T14:27:37Z

67.177.186.240:

When applying [[Help:Extension:ParserFunctions|ParserFunctions]] to [[Help:Template|template]] parameters, a pipe symbol ("|") may be used to provide the empty string as default value, in order to indicate how to handle things if a parameter is or is not passed in.

*<tt><nowiki>{{{1}}}</nowiki></tt>

:;Sample A: <tt><nowiki>{{#if: {{{1}}} | Parameter 1 is not defined, or is defined and non-null/non-empty. | Parameter 1 is null. It contains only empty string(s) or breaking space(s) etc.}}</nowiki></tt>

:;Result: <tt>{{#if: {{{1}}} | Parameter 1 is not defined, or is defined and non-null/non-empty. | Parameter 1 is null. It contains only empty string(s) or breaking space(s) etc.}}</tt>

*<tt><nowiki>{{{1|}}}</nowiki></tt>

:;Sample B: <tt><nowiki>{{#if: {{{1|}}} | Parameter 1 is defined and non-null/non-empty. | Parameter 1 is not defined, or is defined but null. It contains only empty string(s) or breaking space(s) etc.}}</nowiki></tt>

:;Result: <tt>{{#if: {{{1|}}} | Parameter 1 is defined and non-null/non-empty. | Parameter 1 is not defined, or is defined but null. It contains only empty string(s) or breaking space(s) etc.}}</tt>

;Comparison
{| class="wikitable"
! Condition of parameter 1
! Sample A: <nowiki>{{{1}}}</nowiki>
! Sample B: <nowiki>{{{1|}}}</nowiki>
|-
|not defined||'''TRUE'''||''FALSE''
|-
|defined but null/empty||''FALSE''||''FALSE''
|-
|defined and NOT null/empty||'''TRUE'''||'''TRUE'''
|-
|}

The second usage (<nowiki>{{{1|}}}</nowiki>) is often the desired way to handle situations where a parameter exists, but is comprised only of empty space.

==See also==
*[[Help:Extension:ParserFunctions]]
*[[Help:Template]]

[[Category:Help|Parser functions in templates]]

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Help:Parser functions in templates