Jump to content

Help:Templates

From mediawiki.org
Revision as of 06:46, 4 August 2024 by Shirayuki (talk | contribs)
Languages:
PD Note: When you edit this page, you agree to release your contribution under the CC0. See Public Domain Help Pages for more info. PD

If you have standard texts you want to include on several pages, the MediaWiki template feature comes into play. Unlike extensions and media files , there is no central repository for templates. Templates can be newly written or, to save duplicating work already done, exported from another wiki e.g. Wikipedia, and then imported into the target wiki.

Basic usage

Templates are standard wiki pages whose content is designed to be transcluded (embedded) inside other pages. Templates follow a convention that the name is prefixed with "Template:", assigning it to that namespace; besides this, you can create them like any other wiki page.

To transclude a template, you used double open & close curly brackets {{template name}}.

The simplest use of templates is as follows: Create a page called Template:Welcome with the content below: 

Hello! Welcome to the wiki.

You have created your first template! Now, insert the code below in a new page: 

{{Welcome}}

When the new page is viewed, the text "Hello! Welcome to the wiki." will appear instead of {{Welcome}}. The template content is transcluded into the other page, i.e., it is integrated in the page.

You can then insert {{Welcome}} at any point of any page where you wish to welcome someone. Suppose it is used in 100 pages. If you then change the template contents to: 

Hi there! Welcome to this wonderful wiki.

And revisit any of the 100 pages where the template was used, you'll see the new text instead of the original one. In this way, you have changed the content of 100 pages without editing them, because the template is transcluded into these pages.

This is the basic mechanism. There are several additional features of transclusion that enrich this mechanism and make templates very useful.

Ways to invoke a template

Templates can be used in other pages in these ways:

  • {{Name}} — As described above, this text (commonly referred to as a "template call") will be dynamically replaced by the content of the page titled Template:Name (a process called "transclusion") every time the page with the template call is loaded (i.e., viewed by a reader of the wiki). Because the template call remains in the pages's source, any subsequent change to Template:Name will be seen on the page containing the template call. Also, the page will be listed among those that "link to" the template.
  • {{subst:Name}} — When this type of template call is used, it will be replaced by a static copy of the content of Template:Name as of the time the page containing the template call is saved. That is, a copy of the contents of Template:Name will be substituted for the template call. No link is maintained between the page and the template, so each can be edited further without affecting the other. In effect, there is little difference between substituting the content in this way and simply typing it into the page's source "manually". See Help:Substitution for more information.
  • {{safesubst:Name}} — This was introduced to allow for recursive substitution in cases where templates contain calls to other templates or parser functions. See Help:Substitution for more information.
  • {{msgnw:Name}} — This displays the template content as raw wiki syntax (the way ‎<nowiki> does) when the page containing it is viewed. For example, {{msgnw:Template:Thankyou}} displays:

<noinclude> <languages/> </noinclude> '''A little thank you...''' for {{{reason|{{{1}}}}}}. hugs, {{{signature|{{{2}}}}}} <noinclude> [[Category:Template examples{{#translation:}}|{{PAGENAME}}]] </noinclude>

In fact, an ordinary wiki page can also be used as a template, simply by specifying the namespace it resides in, so:

  • {{Template:Pagename}} transcludes the page titled Template:Pagename (equivalent to {{Pagename}})
  • {{Talk:Pagename}} transcludes the page titled Talk:Pagename
  • {{:Pagename}} transcludes the page titled Pagename (i.e., in the main namespace)
    • {{subst::Pagename}} substitutes the contents of the page titled Pagename

If the specified namespace doesn't exist, the full title is assumed to be a template:

  • {{Foo:Bar}} transcludes Template:Foo:Bar

Regardless of what syntax is used, the name of the template can be relative to the current page For example, if {{/bar}} is called on page foo, it will transclude the page foo/bar.

It can also be generated dynamically. For example, {{ {{foo}} }} calls Template:foo and interprets the result as the name of another template to call.

Parameters

To enrich the mechanism of transclusion, MediaWiki allows parameters to be passed to a template when it is transcluded. Parameters allow the template to produce different contents or have different behaviors.

Suppose you wish to insert a little thank you note in the talk page of other users, such as:


A little thank you... for all your effort. hugs, Me


The thank you note will have a reason (in this case, "all your effort") and a signature ("Me"). Your objective is for any user to be able to thank any other user, for any reason whatsoever.

So that the note will look similar everywhere it is used, you can define a template called Template:Thankyou , for example. Although the note should look similar whenever a user thanks another user, its specific contents (i.e., the reason and the signature) will be different. For that reason, you should pass them as parameters. If we ignore the remaining elements to format the box and place the image, the core content of the template will be this: 

'''A little thank you...'''
for {{{1}}}.
hugs, {{{2}}}

Notice the use of {{{1}}} and {{{2}}}. This is the way to identify, within templates, the parameters that will be passed in when the template is used. Note that, within the template, each parameter is surrounded by three braces: {{{ }}}. This is different from normal template name usage.

When using the template on a page, you fill in the parameter values, separated by a "pipe" character (|). MediaWiki allows parameters to be passed to the template in three ways: Anonymously, Numbered, and Named.

Anonymous parameters

To pass in anonymous parameters, list the values of those parameters sequentially: 

{{Thankyou|all your effort|Me}}

In this case, the {{Thankyou}} template receives parameters {{{1}}}=all your effort and {{{2}}}=Me, producing:


A little thank you... for all your effort. hugs, Me


The order in which anonymous parameters are passed in is crucial to its behavior. Reversing the order of the parameters, like so: 

{{Thankyou|Me|all your effort}}

would produce this result:


A little thank you... for Me. hugs, all your effort


Identifying parameters by order (with {{{1}}}, etc.) works only with anonymous parameters. Any parameters identified by name, as shown below, will not be accessible to the template using ordinal numbers.
If an equal sign appears inside the argument to an anonymous template parameter, that parameter may be misinterpreted as a named parameter (which is explained below in this document) treating the text before the equal sign as the parameter name and the text after it as the argument value. This is a common problem when you need to include an external link, or an HTML element with attributes (see task T16235). The workaround is to use named parameters instead, or even numbered parameters as explained in the following section.

Numbered parameters

To pass in parameters by number, identify each parameter when passing it: 

{{Thankyou|2=Me|1=your friendship}}

This time, template {{Thankyou}} receives parameters {{{1}}}=your friendship and {{{2}}}=Me, though they have been supplied in inverse order, and produces:


A little thank you... for your friendship. hugs, Me


This may also be useful when any of the numbered parameters contains an "=" sign.
Examples
{{Thankyou|1=adding “=”|2=Me}}

produces:


A little thank you... for adding “=”. hugs, Me

Warning Warning: This also requires numbering each other parameter.

Named parameters

The third way of passing parameters is by name instead of numbers. In this case, the template contents would be changed to: 

'''A little thank you...'''
for {{{reason}}}.
hugs, {{{signature}}}

Within the template, we use {{{reason}}} and {{{signature}}} to identify each parameter, instead of a number. To pass these parameters by name, identify each parameter when passing it: 

{{Thankyou|signature=Me|reason=being who you are}}

In this case, template {{Thankyou}} receives parameters {{{reason}}}=being who you are and {{{signature}}}=Me and produces:


A little thank you... for being who you are. hugs, Me


Named parameters are case-sensitive, so: 

{{Thankyou|signature=Me|Reason=being who you are|reason=being case-sensitive}}

produces:


A little thank you... for being case-sensitive. hugs, Me


The advantage of using named parameters in your template, besides also being flexible in the order parameters can be passed, is that it makes the template code much easier to understand if there are many parameters.

Spaces and newlines are automatically stripped from the start and end of named parameter names and values, but are preserved in unnamed parameters.

Mixing named and unnamed parameters

If the template supports it, both kinds of parameters can be used in one call.

For example, {{Thankyou|supporting both parameter types|signature=Me}} results in:


A little thank you... for supporting both parameter types. hugs, Me


Be careful when doing this, because it can result in conterintuitive results as unnamed parameter counts are based only on the unnamed parameters, not the named parameters. For example, {{Thankyou|Me|reason=supporting both parameter types}} results in:


A little thank you... for supporting both parameter types. hugs, {{{2}}}


The template is coded to prefer the named parameter for the reason over the unnamed parameter, resulting in the "Me" being lost and no signature being given. This results in a default value of {{{2}}} being shown, as explained below.

Default values

See also: Manual:Advanced templates#Use of parameter default

If you transclude a template that expects parameters, but do not provide their arguments, in this way: 

{{Thankyou}}

in the numbered parameters example above you would get the following:


A little thank you... for {{{1}}}. hugs, {{{2}}}


Since no arguments were passed in, the template presents the parameters themselves, instead of their respective values. In these cases, it may be useful to define default values for the parameters, i.e. values that will be used if no value is passed in. For example, if the template contents are changed to: 

'''A little thank you...'''
for {{{reason|everything}}}.
hugs, {{{signature|Me}}}

then {{{reason|everything}}} defines that if no argument is provided for parameter {{{reason}}}, then the value everything will be used. Similarly, {{{signature|Me}}}, defaults parameter {{{signature}}} to value Me. Now, transcluding the template again without passing any argument results in the following:


A little thank you... for everything. hugs, Me


The value of a parameter can be an empty string. For example, in {{foo|bar=}} or {{foo|bar=|baz=qux}}, the foo template considers the bar parameter to be "". This is different from omitting the parameter altogether, which leaves it undefined and triggers the default value mechanism described above.
If you need to treat an empty string the same way as a missing parameter, you can use a conditional operator through an extension like ParserFunctions. For instance, {{#if:{{{1|}}}|{{{1|}}}|undefined}} returns undefined if the parameter is either undefined or empty, while {{{1|undefined}}} does so only if the parameter is undefined.

Often default values are used to specify alternate names of parameters. For example, if you have {{{a|{{{b|}}} }}}, the template will first look for a parameter named "a". If it is not set, it will use the parameter named "b". If neither "a" nor "b" is set, it will output nothing.

Passing parameters to other templates

If raw parameter syntax is generated by the above template call, and then passed through to another template, it is not interpreted as a parameter. This means that {{Thankyou2 }}, which just calls {{Thankyou }} with no parameters, does not work: {{thankyou2|everything|me}} -> A little thank you... for {{{1}}}. hugs, {{{2}}} .

You instead need to explicitly pass the parameter to the other template, i.e if {{Thankyou3 }} contains 

{{thankyou|{{{1}}}|{{{2}}}}}}

then {{thankyou3|everything|me}} -> A little thank you... for everything. hugs, me } works properly.

This example does not preserve emptiness vs. undefinedness in parameter values - you would need more complicated syntax if you wanted to do that.

Empty vs undefined parameters

The {{t2demo|| a }} (refer to {{T2demo }} ), with a double pipe, sets the first parameter to an empty string instead of leaving it undefined. It produces the output start--middle- a -end, similar to how {{t2demo|1=|2= a }} results in start--middle- a -end. On the other hand, explicitly setting the parameter "2" to "a," results in the first unnamed parameter being left undefined:

{{t2demo|2= a }} results in start-{{{1}}}-middle- a -end

If the second parameter should not be trimmed, it must be unnamed.

Therefore, you can assign an empty string to the first parameter, but you cannot leave it undefined.

Making emptiness and undefinedness equivalent

Good template coding practices result in passing an empty string to a parameter working the same as not assigning any value. This makes things easier and more consistent.

For example, using p= can show that a template has a parameter "p" that doesn't have a value yet.

To make an empty string and an undefined value equivalent, use the following approaches:

  • Use {{{p|}}} exclusively instead of {{{p}}} or q where "q" is a non-empty value.
  • Use conditional checks like {{#if:{{{p|}}}|..{{{p}}}..|..}}, to ensure {{{p}}} is only used when it has a value.

If for some reason you want to treat undefined parameters differently from empty parameters or any other possible value you can compare the same parameter twice with different defaults, i.e {{#ifeq:{{{foo|bar}}}|{{{foo|baz}}}|parameter is defined|parameter is undefined}}.

Using equals signs in unnamed parameters

Unnamed parameters can include equals signs, but this must be done indirectly. Here are some methods using template:T1demo:

Default Value for Undefined Parameter

Assign a default value to an undefined parameter: 

{{T1demo|{{{1| a=b }}}}}

This renders as: start a=b end.

Using the {{=}} parser function

Use a parser function that safely includes an equals sign: 

{{T1demo| a{{=}}b }}

This renders as: start a=b end.

HTML Entities

Replace the equals sign with an HTML entity for display: 

{{T1demo| a=b }}

This renders as: start a=b end.

This renders correctly without affecting the other parameters.

Handling unmatched curly and square brackets

Unmatched curly brackets ({{, }}) or square brackets ([[, ]]) must be inside nowiki tags or use HTML entities:

  • Rendering curly brackets have two options:
    • Use <nowiki>{{</nowiki> or &#123; for {
    • Use <nowiki>}}</nowiki> or &#125; for }.
  • Use &#91; for [ and &#93; for ].

Below are some examples:

Unmatched curly brackets
{{T1demo| <nowiki>{{</nowiki>content<nowiki>}}</nowiki> }}

This correctly renders the braces without breaking the template.

Unmatched square brackets
{{T1demo| text [link] more text }}

This correctly renders the braces without breaking the template.

This renders as: start text [link] more text end

Unmatched pairs not placed in nowiki tags either prevent template expansion or are taken as closing braces for the template call.

Below are some examples: 

{{T1demo|abc]]def[[ghi}}

This will not expand correctly because of unmatched brackets.

The correct use: 

{{T1demo|abc<nowiki>]]</nowiki>def<nowiki>[[</nowiki>ghi}}

This renders as: startabc]]def[[ghiend

Template-generated brackets

An alternate technique for passing arguments with unmatched brackets is to wrap them in another template. In that situation, (which exists with {{(( }} and {{)) }}) on this wiki), the unmatched brackets will be rendered literally, and not decoded as another template call. For example: 

{{t1demo|{{((}}t1demo{{))}}}}

results in: start{{t1demo}}end

When substituting a template, template inclusions are parsed once when the subst happens (with the same caveats explained above) and then a second time when rendering the resulting wikitext. For example: 

{{subst:((}}t1demo|foo}}

will expand on save to: 

{{((}}t1demo|foo}}

which will then render as: 

startfooend

If the wikitext generated via the first subst itself includes "subst:" syntax it will not be processed on the same save, but may be on the next save. This technique may be used to implement recursive substitutions that take multiple saves to evaluate.

Using pipes in parameter values

A parameter value cannot contain a pipe character (|), because it would be interpreted as the end of that parameter and the start of the next parameter. This can be worked around by using the parser function {{!}}, or the HTML entity &124;. The two methods of doing this have slightly different behavior, which can be relevant in some corner cases like when a template is producing wikitable syntax.

Example: {{T1demo|abc|def}} produces: startabcend

The "def" doesn't display because it is treated as part of another unnamed parameter, which the template does not use.

{{T1demo|abc{{!}}def}} produces: startabc|defend

The "def" displays properly.

{{T1demo|abc|def}} produces: startabc|defend

The "def" displays properly again.

Formatting template calls using extra parameters

Since templates ignore parameters they are passed but do not handle specifically, they can be used as a way of a adding extra whitespace or unused content to the template call.

For example: 

{{template name|foo|bar|baz|mumble|quux}}

is equivalent to, assuming the template doesn't recognize SPACEN as a parameter name: 

{{template name|SPACE1=
|foo|SPACE2=
|bar|SPACE3=Random stuff
|baz|SPACE4=
   |mumble|SPACE5=
  quux
}}

It is also possible to use the same name for each spacer (often the empty string), but this will populate Category:Pages using duplicate arguments in template calls, which many wikis prefer to keep empty to catch instances of user error.

This can be used to make the template render in a way similar to its output, like showing each row of w:Template:Chess position on its own like to make the wikitext also look like a chessboard.

Tracking parameter usage

See also: Help:Tracking categories


It may be wise for a template to add a link or category to a page if a certain parameter or combination of parameters is used, to make if possible to easily determine what pages are using a given parameter, and thus what the impacts of changing that parameter in the template would be.

Evaluation process

This is an advanced topic which you can skip unless you need it.

Generally speaking, template parameters are substituted into the template after tokenization, but as is. They are not evaluated until they are used.

This has a few consequences:

  1. If you have a Template:Start containing {{mytemplate, and a Template:End containing |foo=bar}}, and put {{start}}{{end}} on a page, mytemplate isn't transcluded, because tokens like "|" cannot be added by a template and keep their special meaning in templates. You can still use templates to control the name of a parameter or template, but you cannot split a template call amongst multiple templates.
  2. Dead-code elimination: If you make a template call like {{foo|{{DISPLAYTITLE:Bar}} }}, and Template:Foo does not contain {{{1}}}, then the DISPLAYTITLE is not used, since it is only evaluated when needed, and there is no parameter to substitute it into, so it is never evaluated. This usually comes into play when using Extension:ParserFunctions , and can be especially noticed when used in combination with the int: magic word that varies by user language. This isn't perfect, and in some cases even if the result of expanding a template is not used (because it is part of an if statement condition, for example), the process of evaluating it can still have side effects. For example, any links produced or other templates used will still be added to Special:WhatLinksHere even if they are not displayed.


Template parameters are pass by value, which means a template cannot modify its arguments. Parameters are treated as associative array, and parameter names are evaluated before parameter values. If the same parameter name is given more than once (either as named or unnamed), only the last instace is used, and the page is added to Category:Pages using duplicate arguments in template calls.

Template calls starting with the magic word subst: or safesubst: are evaluated in a separate first pass that only happens at save time, along with ~~~~ and links using the pipe trick. If they cannot be evaluated during the first pass, subst: calls are ignored, and safesubst: are treated as if a normal template.

Many but not all parser functions, parser tags and trancluded special pages are not directly included like templates but instead are replaced by a "strip marker". This means you cannot manipulate the results with parser functions like padleft: or similar functions from extensions, as they see the strip marker instead of the result of the parser function.

Recursion in templates

Including a template in itself won't throw MediaWiki into infinite recursion. MediaWiki will stop the recursion with the template's name in bold. For example, if the content of Template:Aaaa is a {{Aaaa}} z, it'll display "a a Template loop detected: Template:Aaaa z z".

This safeguard precludes a potentially useful template idiom where a template self-normalizes its own calling arguments. In this forbidden example template:d can either be called {{d|20200311}} or {{d|y=2020|m=3|d=11}}. If called in the first manner, it recurses into itself with the second argument structure (obtained using string parser functions), which then follows a unified processing path. 

{{#if:{{{1|}}}|{{d|y={{#sub:{{{1}}}|0|4}}|m={{#sub:{{{1}}}|4|2}}|d={{#sub:{{{1}}}|6|2}}}}|<!-- processing path with arguments y,m,d regardless of original call pattern -->}}

If template:d is modified to recurse into template:d/2 and template:d/2 is an identical manual copy of template:d this idiom works fine as the self-recursion safeguard operates dynamically and not statically.

A feasible way for the MediaWiki software to loosen the self-recursion rule would be to require that each recursive call have a distinct argument count from all previous active calls, at most once recursing with the argument count non-decreasing. That would provide a strong guarantee against infinite self-recursion while enabling useful idioms such as the one described here in a flexible manner.

If the processing path is of low complexity, a simple solution using only one template is to handle each calling convention on a separate if/else branch, duplicating the logic of the processing path within each case. If the processing path is more complex, each call-structure case can delegate to an implementation template with a unified call structure which provides the final template behaviour.

Tables in parameters

Since the pipe character (|) and equality sign (=) have different meanings in template calls and wikitables, in order to use table markup in the value of a template parameter one generally needs to "escape" those characters (i.e., protect them from interpretation as template markup) using special sequences:

  • the built-in magic word {{!}} provides an "escaped" version of | since MediaWiki 1.24
  • the built-in magic word {{=}} provides an "escaped" version of = since MediaWiki 1.39

Before the introduction of these magic words, many wikis used templates to accomplish the same things. On such a wiki, the magic words take precendence over the same-named templates.

Example table

A B C
A1 B1 C1
A2 B2 C1

Table code: 

{| class=wikitable
!A!!B!!C
|-
|A1||B1||C1
|-
|A2||B2||C1
|}

Escaped table code: 

{{(!}} class{{=}}wikitable
!A!!B!!C
{{!}}-
{{!}}A1{{!}}{{!}}B1{{!}}{{!}}C1
{{!}}-
{{!}}A2{{!}}{{!}}B2{{!}}{{!}}C2
{{!)}}

Note that the first left-brace ({) is interpreted as a literal left-brace character because it is immediately followed by the {{!}} magic word. Similarly, the last right-brace (}) is interpreted as a literal right-brace character because it is immediately preceeded by the same magic word. However, in some cases these brace characters do cause problems, so some wikis provide templates for escaping these characters, as well:

  • the template call {{(}} might provide an "escaped" version of {
  • the template call {{)}} might provide an "escaped" version of }

Some wikis go even further and provide other convenience templates like {{(!}}, {{!)}}, {{!!}}. On such a wiki, the code can be simplified a bit to this form: 

{{(!}} class{{=}}wikitable
!A!!B!!C
{{!}}-
{{!}}A1{{!!}}B1{{!!}}C1
{{!}}-
{{!}}A2{{!!}}B2{{!!}}C2
{{!)}}

Controlling template inclusion

By default, a template's content is displayed in its entirety, both when viewed directly and when included in another page. The template's page when viewed directly appears exactly as the template would render without any parameters. If the template requires parameters to function properly, this will result in raw wikitext syntax or errors as a result of them being missing. For example:

  • If a parameter has no default value, it shows as the literal text {{{1}}}, indicating the template needs a parameter.
  • If a parameter has an empty default value (it is written as {{{1|}}}), it displays nothing, which achieves the intended effect but lacks clarity for self-documentation. Using a non-empty default value like {{{1|image}}} could clarify a parameter's role, especially for templates involving images.
  • If a parameter without a default is passed to the #expr parser function, it results in an error message: "Expression error: unrecognized punctuation character '{'."
  • If a template creates a table, it's helpful for the template page to show the table's structure rather than the wikitext used to make it.To do this, the table syntax isn't enclosed in tags, and each table element includes both ‎<noinclude>...‎</noinclude> and ‎<includeonly>...‎</includeonly> parts where needed.

However, you can control which parts of a template will be seen and included by the use of the ‎<noinclude>, ‎<includeonly> and ‎<onlyinclude> tags.

Anything between ‎<noinclude> and ‎</noinclude> will be seen only when the template's page is being viewed directly, but not when it is included in another page. This is useful when you want to include text or code in a template that you do not want to propagate to any pages which include it, such as:

  • Category links when categorizing the template itself
  • interlanguage links to similar templates in other languages
  • Explanatory text about how to use the template. It's a common pattern on some wikis to use a template like {{Documentation }} to transclude the documentation from a subpage of the template. For example, Template:Void is documented at Template:Void/doc.

Likewise, anything between ‎<includeonly> and ‎</includeonly> will be processed and displayed only when the page is being included, but not when the template page is being viewed directly, and is useful in situations such as:

  • Categorizing pages which include the template. Note: when changing the categories applied by a template in this fashion, the categorization of the pages which include that template may not be updated until some time later: this is handled by the job queue . To force the re-categorization of a particular page, open that page for editing and save it without changes.
  • Ensuring that the template's code is not executed when viewing the template page itself. Typically this is because it expects parameters, and its execution without parameters has an undesired result.

Everything outside ‎<noinclude> and ‎<includeonly> is processed and displayed normally; that is, both when the template page is being viewed directly and when the template is included in another page. The focus is on what is inside these two tags.

Everything outside ‎<onlyinclude> tags is discarded in the transclusion. Even sections tagged includeonly are discarded in the transclusion unless they are also tagged as onlyinclude. The focus is only on what is inside this tag.

For example, if a page like Help:Templates/onlyinclude demo has the wikitext: 

abc<onlyinclude>def</onlyinclude>ghi<includeonly>jkl</includeonly>

The result of transcluding it is def.

Nesting of these tags is also possible.

The three partial transclusion tags enable all possible combinations of what is processed and rendered. Comments also fill a role. Inclusion tags are respected when using {{subst:templatename}}, but they are not respected when using {{msgnw:templatename}} as that displays the raw wikitext without any processing.

Section transclusion

To transclude different sections of a template on different pages, you can wrap the content in onlyinclude tags and use an if statement on parameters to select which section.

Consider "Template:Example" with this wikitext: 

== Section 1 ==
{{#ifeq:{{{1|1}}}|1|
Content of section one.
}}
{{#ifeq:{{{1|2}}}|2|
== Section 2 ==
Content of section two.
}}

This will render both sections on the example page itself, and allow other pages to transclude the first section with {{example|1}} and the second section with {{example|2}}.

Another approach is to use literal parameter syntax instead: 

{{{section1|
== Section 1 ==
Content of section one.
}}}
{{{section2|
== Section 2 ==
Content of section two.
}}}

Transclude the first section with {{example|section2=}} and the second section with {{example|section1=}}. If neither parameter is used, then both sections will display.

A third approach is to use Labeled Section Transclusion.

Organizing templates

For templates to be effective, users need to find them, and find out how to use them.

To find them, users can:

  1. Click Special pages > All pages
  2. In the Namespace: list, choose Template and click Go.

To give usage information, include an example like this one on the template page: 

<noinclude>
== Usage ==
Welcome users:
{{Thankyou|reason=your reason|signature=your signature}}
</noinclude>

Then, an editor can simply copy and paste the example to use the template.

While editing a page, a list of all templates used is available under the editing form, in a collapsible section titled "Templates used on this page:" (also named "Templates used in this preview:", or "Templates used in this section:" depending on the context). This list provides a convenient link to the template's page, as well as information about its protection status. Redirected templates are shown in italics, with the redirect target added as a separate list item.

Linking to a template

A template page can be linked to like any other wiki page. For example, the link Template:Navbar is generated using the wikicode [[Template:Navbar]].

On many wikis, Template:Tl can be used to provide a link to a template formatted in a way that shows the "double curly-braces" wikicode necessary to transclude the template without actually doing the tranclusion. For example, the code {{tl|Navbar}} may be used to create the link {{Navbar }}.

This construct is commonly used when referring to templates in template documentation, on help pages, and on talk pages. The same effect can be achieved by using {{[[Template:Navbar|Navbar]]}}, but the {{Tl }} approach involves much less typing. On any given wiki the Tl template, if it exists, may or may not render the text in a "code" element or as monospace type. If not (as on this wiki), another similarly named template may do so. See, for example, the "See also" section of our Template:Tl documentation.

Template naming

The name of a template is case-sensitive excluding the first character.

You make redirects for alternate capitalizations. For example, if a template is named "AdminAbbr", you can create a redirect named "Adminabbr". This way, the template can be called with either {{AdminAbbr}} or {{adminabbr}}. If an editor prefers a mix of upper and lower case for clarity, they can use functions like lc or uc. For instance, instead of {{CURRENTINTERNETTIME}}, they could use {{ {{uc:CurrentInternetTime}} }}

Because template names are interpreted in the same way to the names of other pages, underscores are replaced with spaces, and any text after a number sign (what would be a anchor in a standard link) is ignored.

An underscore _ can be alternative to a blank space.

Possible uses of templates

Templates can be used for any situation in which one wants two or more pages to contain identical or similar content that is edited together rather than independently. They can be used to:

  • Provide structured elements on many pages, like infoboxes, maintenance templates, navigational boxes, etc.
  • Perform calculations used as a programming tool on various pages, like w:Template:Sum.
  • Build composite pages that display the content of multiple existing pages together, like w:WP:Village pump (all) which includes content from each section of the village pump. The content of these pages can either be shown individually, or together, but the revision history, watchlist, etc. will only pick up changes to the transcluded pages and the raw wikitext of the composite page itself, not implicit changes to the composite page.
  • Share some content between a few related pages. For example, the list at Help:Preferences#Beta features is duplicated at Beta Features#Current Beta Features. While on MediaWiki.org that is built using Extension:LabeledSectionTransclusion instead, it could have been done using a template.
  • Store content referenced multiple times on the same page, so it only has to be written and calculated once. For example w:Template:Cite Monumentenregister/URL is called twice by w:Template:Cite Monumentenregister in two different places, and using another template means the URL pattern only has to be written once in the base template.
  • Use templates as a programming element to generate a loop: if Template:A calls Template:B 10 times with different parameters, then that crudely simulates a for loop. If Template:B calls Template:C 10 times, then you have a nested loop of 100 calls of Template:C. But keep in mind that it is easy to run into the template limits when using templates as advanced programming constructs, and using Scribunto is generally clearer and easier to follow.

Copying from one wiki to another

It is possible, if allowed by the wiki configuration to transclude templates from other wikis. This configuration setting is disabled on Wikimedia wikis. Otherwise, you need to manually copy the template and its dependencies from the source wiki to the destination wiki to use it.

Templates often require CSS or other templates, so users frequently have trouble copying templates from one wiki to another. The steps below should work for most templates.

MediaWiki code

If you have import rights (specifically importupload) on the new wiki:

  1. Go to Special:Export on the original wiki, and download an .xml file with the complete history of all necessary templates, as follows:
    • Enter the name of the template in the big text box, e.g. "Template:Welcome". Pay special attention to capitalization and special characters — if the template name isn't exactly correct, the export may still occur but the .xml file will not have the expected data.
    • Select the box "Include templates".
    • Select the box "Include only the current revision, not the full history".
    • Click "Export".
  2. Go to Special:Import on the new wiki and upload the .xml file.

If you don't have import rights on the new wiki:

  1. Go to the template you want to copy from the original wiki. Go to the edit page, and copy all the wikitext
  2. On the new wiki, go to the page with the same name as the template you copied. Hit create/edit and paste the wikitext you copied. In the edit summary of each template, link to the original page for attribution.
  3. Back in the original wiki at the edit window, below the edit box, look at the list of "Templates used on this page". For each template listed follow these instructions. Also do that for any template used by any of these templates, and so on.

This will copy the entire code necessary, and will suffice for some templates. Note that only page elements parsed in rendering the page get exported, consequently documentation subpages are not exported as part of this process. If it doesn't work also check for red links listed under "Pages transcluded onto the current version of this page:", below the edit box. If there are any repeat the above steps for these as well and also copy the code in the modules.

After successfully importing the template and all its linked templates from the other wiki, edit it to change customisations to suit your wiki. For example to change a logo, remove redundant categories or red links.

Extensions

An extension often used in templates is ParserFunctions. Visit page Extension:ParserFunctions and check if any of the functions listed there are used in the templates you've copied. If so, you have to install the ParserFunctions extension. To install it, you'll need system admin access to the server of your MediaWiki installation.

Another dependency that may be used in templates, especially those on Wikipedia, is Lua. Having {{#invoke: }} in template code is a good sign for it. In case it's used, you need to install the Scribunto extension and system admin access is required too. See that page for more instructions about installing and using the extension.

CSS and JavaScript code

Besides MediaWiki code, many templates make use of CSS and some rely on JavaScript to work fully. If the copied templates are not behaving as expected, this may be the cause. To copy the required CSS and JavaScript to your wiki you'll normally need to have admin privileges, because you'll be editing system messages in the "MediaWiki:" namespace.

  1. Look for the use of CSS classes (text like class="foobar") in the template text. If those classes appear in "MediaWiki:Common.css" or "MediaWiki:Monobook.css" on the original wiki, copy those classes to "MediaWiki:Common.css" on the new wiki and check if the template is now fine.
  2. If the copied template is still not working as expected, check if there is code in "MediaWiki:Common.js" or "MediaWiki:Monobook.js" on the original wiki. If so, you can try copying it to "MediaWiki:Common.js" on the new wiki. Normally, it is a good idea to only copy code from trusted sources, and browse the code to identify and select the relevant parts. You may find comments that can serve as clues to identify the functionality of each part.

Redirection

If a page uses a redirect as a template, the redirect is resolved before processing the template and the target is used instead. This won't work if the target doesn't exist (a broken redirect), or is itself a redirect (a double redirect).

A page that just includes another page as a template might look like a redirect, but there are several differences between them:

  • The header of the result displays the title of the page it came from.
  • No "Redirected from" message is shown.
  • Buttons like edit, watch, talk, history, "what links here," and "last modified" point to the referring page. To access the target page, use a section edit link and navigate from there.
  • Unless includeonly and/or noinclude tags are used, the referring page shares the same categories as the target page.
  • "Double redirects" work when one or both are this type of pseudo-redirect.
Embedding works on pages that support redirects and doesn't work on pages without it.

Parser functions

Main page: Help:Parser functions

MediaWiki also supports parser functions, which function similarly to templates but follow slightly different syntax:

  • Parser functions utilize a ":" instead of the initial "|".
  • An edit page does not display parser functions used on that page.
  • There is no "What links here" feature for parser functions to identify the pages where they are utilized.
  • Parser functions templates do not generally accept named parameters, so equal signs generally have no special significance. For example:
{{ #if: not blank | x=abc }} gives x=abc

See also

General template usage

Special constructs used in templates

Other relevant information

Retrieved from "https://www.mediawiki.org/w/index.php?title=Help:Templates&oldid=6686855"