Editing Help:Transclusion (section)

===Template parameters<span class="anchor" id="Template transclusion"></span>===
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{{further|Help:Template#Parameters}}
{{for|a quick guide to templates|Help:A quick guide to templates}}

The most common use of transclusion on Wikipedia is for [[Help:Template|templates]]. Templates are specially designed pages intended to be included in other pages using either transclusion or [[Help:Substitution|substitution]]. The standard syntax for transcluding a template titled {{Xtn|Template:Pagename}} is <syntaxhighlight lang="wikitext" inline="">{{Pagename}}</syntaxhighlight>.

Additionally, many templates support [[Parameter|parameters]], which are variables that allow templates to function in different ways by passing specific values, also termed ''[[Parameter (computer programming)#Parameters and arguments|arguments]]''. Templates may have no parameters, use a fixed number of parameters, or support a variable number of parameters. The number of parameters a template can accept ranges from one to multiple, depending on its design.

The exact syntax for using parameters varies by template. However, for a hypothetical template titled {{Xtn|Template:Pagename}} that accepts three parameters, the general format would be:

<syntaxhighlight lang="wikitext" inline="">{{Pagename|parameter1|parameter2|parameter3}}</syntaxhighlight>

{{shortcut|WP:UNNAMED|WP:POSPARAM|WP:POSITIONAL}}
Where each parameter in a template can be substituted with either a <code>value</code> or a {{Para|parameter name|value}} format when used in practice. Notice that each parameter is separated by a [[vertical bar]] (<code>|</code>). Parameters that take the form <code>value</code> are called ''unnamed'' or ''positional parameters'', while those in the form {{Para|parameter name|value}} are known as ''named parameters''. With unnamed parameters, the first, second, and third parameters correspond to {{Para|1}}, {{Para|2}}, {{Para|3}}, respectively, etc., in [[Wikipedia:Template documentation|template documentation]]. Unnamed parameters must be provided in the correct order and are best placed before named parameters.{{Refn|Otherwise using <code>value</code> on its own will not work, and the unnamed parameters must be called using their 'names', such as {{para|1|value}}, if named parameters precede them.|group=lower-alpha}}

For example, using the {{Xtn|[[Template:Collapse top]]}} with two unnamed parameters and one named parameter:

: {{y}} <syntaxhighlight lang="wikitext" inline="">{{Collapse top|This is the title text|This is a custom warning line|left=true}}</syntaxhighlight>
: {{y}} <syntaxhighlight lang="wikitext" inline="">{{Collapse top|left=true|1=This is the title text|2=This is a custom warning line}}</syntaxhighlight>
: {{n}} <syntaxhighlight lang="wikitext" inline="" style="background-color:#ffdad3;">{{Collapse top|left=true|This is the title text|2=This is a custom warning line}}</syntaxhighlight>

In this case, <code>This is the title text</code> and <code>This is a custom warning line</code> are the values of unnamed parameters {{Para|1}} and {{Para|2}}, while <code>true</code> is the value assigned to the named parameter {{Para|left}}. The last example shows how unnamed parameters should not be used after named parameters without their 'name'. Although this example includes three parameters, {{Xtn|[[Template:Collapse top]]}} can accept a variable number of parameters.

For more details, see [[Help:Template]]. Additionally, [[Wikipedia:Template index]] provides a categorized list of templates, including those for mainspace and other namespaces, along with a search function. Template parameters also play a role in the {{section link|#Parametrization method}} of {{Section link|2=Selective transclusion|nopage=y}}, allowing for more dynamic content inclusion.