Help:Template

{{Subtemplate|{{#if:||Arg1={{{Arg1}}}}}}}

Unfortunately, this won't work; it instead passes "Arg1={{{Arg1}}}" as parameter 1. As previously stated in this article, with templates, parser functions, and magic words (i.e. anything that uses the {{...}} syntax), when specifying an argument, MediaWiki only recognizes equal signs or pipes if they are outside a nested template-like call in the argument. In other words, it doesn't process equal signs or pipes that are the result of a template-like call.

Workaround using Extension:VariablesExtension and Extension:Loops

(Note: Loops also requires Extension:ParserFunctions to function.)

Since variables from Extension:VariablesExtension are automatically passed to a subtemplate, we can just convert all of our template parameters to variables. For example, this will convert unnamed parameters:

{{#vardefine:i|1}}{{
	#while:
	|{{{{{#var:i}}|}}}
	|{{#vardefine:{{#var:i}}|{{{{{#var:i}}}}}}}{{#vardefine:i|{{#expr:{{#var:i}}+1}}}}
}}{{subtemplate}}

Now we would program our subtemplate to use {{#var:1}} as opposed to {{{1}}}. Here's another example, but with named parameters like "Arg1", "Arg2", and so forth:

{{#vardefine:i|1}}{{
	#while:
	|{{{Arg{{#var:i}}|}}}
	|{{#vardefine:Arg{{#var:i}}|{{{Arg{{#var:i}}}}}}}{{#vardefine:i|{{#expr:{{#var:i}}+1}}}}
}}{{subtemplate}}

Now one would use {{#var:Arg1}}, {{#var:Arg2}}, etc. The downside of this method is that you might have to completely redesign your subtemplate to function with variables as opposed to parameters.

Workaround using Extension:DynamicPageList

The third-party Extension:DynamicPageList allows for what is called a surrogate template. This is an even easier way of passing all parameters. For example, you would put this in your top template:

{{#dpl:|title={{PAGENAME}}|include={TemplateName}Sub }}

This would call Template:TemplateNameSub with all of the arguments that were originally included with the original template call. More information can be found at the DPL:Manual - DPL parameters: Controlling output volume.

Template tag lay-out

To have a desired template tag lay-out, especially in the case of many parameters, additional dummy parameters can be used with a newline, spaces, and/or comments. In the case of unnamed parameters, this means that some parameter numbers are not used in the template content, so that their values, present in the template tag, do not affect the rendering of the template. For example, using Template:t3d containing "{{{1}}} {{{2}}} {{{3}}}<br /> {{{5}}} {{{6}}} {{{7}}}<br /> {{{9}}} {{{10}}} {{{11}}}",

{{t3d |a|b|c| 1
      |d|e|f| 2
      |g|h|i| 3
}}

gives:

a b c
d e f
g h i

If parameters are named, dummy parameters can easily be inserted at any time. If they are unnamed, then, to avoid renumbering, one can insert named parameters: any text including an equals sign will do, if the text on the left is not one of the parameter numbers: this text is interpreted as the name of an unused parameter, hence ignored.

Example:

Using template:Chess position ( talk edit history links )

{{chess position|=

 8 |rd|nd|bd|qd|kd|bd|nd|rd|=
 7 |  |pd|pd|pd|pd|pd|pd|pd|=
 6 |pd|  |  |  |  |  |  |  |=
 5 |  |  |  |  |  |  |  |  |=
 4 |  |pl|  |  |  |  |pl|  |=
 3 |  |  |  |  |  |  |  |bl|=
 2 |pl|  |pl|pl|pl|pl|  |pl|=
 1 |rl|nl|bl|ql|kl|  |nl|rl|=
    a  b  c  d  e  f  g  h

|30}}

which gives

In this example, the 1 to 8 row numbers and a to h column numbers (as well as their surrounding spaces and newlines) in the parameter list are hidden within a dummy parameter (with an empty name before the equal sign).

The template generates an HTML table where each cell contains an image whose name is dynamically generated from the 64 first automatically numbered parameters (there are intermediate parameters within the numbered list, but as these dummy parameters are named explicitly, they don't increment the parameter number used to generate default parameter names. So the parameter with autogenerated name "1" effectively contains the "rd" value).

The template is then called with a parameter list that contains:

• 65 parameters automatically named from "1" to "65" (64 parameters for the cells content, and the 65th for the image width),
• and a dummy named parameter (whose name is an empty string, and whose effective value results from the last assignment with the chessboard column names a to h and the surrounding spaces and newlines), which is not used in the internal template content.

Note also that all parameters are trimmed, so the parameter with autogenerated name "9" (at position a7 on the chessboard above) is assigned the empty string value.

Relative name for transcluded page

A page A can transclude a subpage A/B using {{/B}} or, with more control over the name of the page to be transcluded, this name can be constructed from {{PAGENAME}}.

This allows copies of the same wikitext in different pages to transclude different pages. Thus for example, the same wikitext, adapted from [4], containing a list of calls {{/lang|..}}, can be used in various ways on different pages, for example List of Wikipedias/lang/demo‎ and List of Wikipedias/local names‎, by varying the content of the subpage. A transcluded page need not use all the specified parameters. Two pages can share the same transcluded page using a redirect.

Template page

Without noinclude and includeonly parts the following are identical:

• the rendering of the wikitext of the template (this is on the template page, and would be the same in other pages with that wikitext, except for page-dependent variables)
• the rendering of the template on a page that calls it without parameters

Thus, the defaults are shown, e.g., Template:T 1 containing "abc{{{1|def}}}ghi{{{1|jkl}}}mno" shows the same as {{t 1}}: "abcdefghijklmno".

Template page if no defaults have been specified

In simple cases this corresponds to treating the parameter tags as ordinary text, for example:

"{{t2demo}}" (using Template:t2demo containing start-{{{1}}}-middle-{{{2}}}-end<noinclude>[[Category:Demo template]]</noinclude>) gives start-{{{1}}}-middle-{{{2}}}-end

Similarly, if part of the parameters is undefined, only those show up as {{{parameter number or name}}}.

However, often the rendered page produces a seemingly arbitrarily mutilated version of its content:

• #expr and #ifexpr applied to an expression containing a parameter tag without default produces an error message. For example, a template that doubles parameter {{{1}}} with the wikitext {{#expr:2*{{{1}}}}} gives Expression error: Unrecognised punctuation character "{".

For parameters without default a workaround is less needed because the result in the case a parameter is undefined is of limited use anyway. If one wants it anyway one can put nowiki tags around the parameter; for the first example this gives "{{{1}}}p".

Less surprising, but nevertheless limiting the usefulness of the result are:

• #if applied to a parameter tag without default produces the then-part, the else-part is not shown.
• #ifeq typically produces the else-part only.
• Variable tags are not shown, but evaluated.
• A switch typically shows the default only.

In such cases includeonly can be used to avoid uninformative and messy rendering on the template page, but either way a disadvantage during template development is that preview does not (meaningfully) reflect changes in the parts of the page outside the noinclude tags (i.e. the included parts). Therefore it can be useful to provide representative default values, even if that is only done temporarily during development of the template.

With noinclude an informative template page can be produced, containing more demos and test cases than just the single default set. Typically, the noinclude-part of a template page contains examples including or substituting the template. Changes in the working of the template (i.e. changes outside the noinclude-part) are not yet effective in these examples in preview and, in the case of substitution, in "show changes". However, they are reflected in the rendered page after saving.

Some formatting aspects may show up which are not readily seen from the edit box.

A parameter value depending on parameters

As mentioned above, if a parameter is left undefined, the triple braced parameter name in the result does not function as a parameter if the page is called as a template from another page; if it should, do not omit the parameter value but specify it in terms of a parameter of the calling page; compare:

• {{t2ademo|b}} (using Template:t2ademo containing {{t2demo|a}}) gives start-a-middle-{{{2}}}-end
• {{t2a1|b}} (using Template:t2a1 containing {{t2demo|a|{{{1}}}}}) gives start-a-middle-b-end.
• Similarly, {{t2a2|b}} (using Template:t2a2 containing {{t2demo|a|2={{{1}}}}}) gives start-a-middle-b-end. See also below.

The most straightforward way of expressing a parameter value in terms of a parameter is using the same name and making it equal, e.g. {{Lan is|lr=af|le={{{le}}}}} in Template:Lan is mr.

Empty vs. undefined

{{t2demo||a}} makes the first parameter equal to the empty string rather than leaving it undefined: it gives start--middle-a-end. By treating the second unnamed parameter as a parameter with the name "2", the first unnamed parameter can be left undefined.

Example: {{t2demo|2=a}} gives start-{{{1}}}-middle-a-end.

If the parameter is used in a tag like <font size> the default text may give invalid code that is conveniently ignored, rather than resulting in perhaps ugly code being rendered (but this may depend on the browser). See e.g. Template talk:Fontsize.

Parameter names (as opposed to template names) are case-sensitive, even with respect to the first letter, and spaces are distinguished from underscores. The empty string is also a valid parameter name, see Template:T empty string as parameter name.

Parameter 02 is distinguished from parameter 2: using Template:t pl0 containing "{{{1}}}{{{2}}}{{{02}}}", {{t pl0|5|6|7}} gives 56{{{02}}}

Note that parameters in the system messages (MediaWiki namespace]] are written differently: as $1, $2, etc.

msgnw

The prefix msgnw (short for "message, nowiki") is used to display within a page, more or less, the wikitext of another page. Differences are:

• numbered and unnumbered lists are rendered as such instead of displaying # or * signs
• (with the new preprocessor) comments are removed
• a single newline is displayed as a blank space (this is especially disturbing the format of the wikitext of tables, and occurs even though newlines are significant in wikitable syntax)

To avoid most of this processing and to format the text appropriately, use the following to surround the transclusion in pre tags:

<{{p1|pre>}}{{msgnw:PageToTransclude}}{{p1|</pre}}>

Note, however, that comments will still be removed.

This function has been used for displaying the wikitext of a template which is active on inclusion. However, with the introduction of noinclude tags, msgnw displays a mix of that with wikitext for rendering the template page itself, with these and includeonly tags.

For example, for template:msgnw demo ( talk edit history links ):

"{{msgnw:Msgnw demo}}" gives " <includeonly>*abc '''def''' ''ghi'' &le;

• [[jkl]] {{t1demo|p}} [[{{tc}}]]

1. a
2. b

jkl mno </includeonly><noinclude>[[Category:Demo template]]</noinclude>" [5]

Usage

A template is useful for any text for which one wants a copy in two or more pages, and there is no need for each copy to be edited independently to adapt it to the page it is in. Since parameters can be used, versions may to that extent even be different, and parameter values can be edited independently for each. Templates are not only convenient, but they can also "force" a useful uniformity. See also advantages of subprograms.

A template can also provide structure (e.g. a table structure, colors, and other formatting) while the content varies (fully or partly) through parameters and variables.

A template can also carry out computations, comparisons, etc. using ParserFunctions, where the result(s) vary again through parameters and variables. See e.g. Category:Mathematical templates.

Typical applications are:

• template messages such as w:en:Template:stub
• Navigational templates such as w:en:Template:europe, sometimes listed in a directory such as w:Wikipedia:navigational templates
• infoboxes, each time showing the same kind of information in the same format, but each time for a different case, using parameters, e.g. the w:en:Template:Infobox Countries.
• provide cross-language portability of texts which are largely internationally the same, but contain some standard terms different in each language; the standard terms are replaced by {{..}} referring to template pages which have the same name but localised content in each language. This is applied in Wiktionaries for names of languages, terms like "noun", etc.; it is also applied for taxoboxes, see e.g. w:en:Template:Familia and w:fr:Modèle:Familia.
• allow a composite image, composed of a table of images, to be specified by a template tag which itself has a corresponding table-like lay-out, see w:Template:Chess position and w:Template:Game of Go Position (the latter example also shows that the number of parameters a template can have is quite large, in this case 362). Newlines in parameter values provide the lay-out of the template tag, but they are not allowed in image names, therefore they are put within comment tags; alternatively, dummy parameters could be used on these positions.

Various combinations are possible. E.g., the last two could be combined, so that e.g. every language version of Wikipedia has the same Infobox Countries template (for each project a copy, because the template mechanism can not import across projects), which has parameters for the data, and refers to templates with translations of standard terms.

See also Help:Advanced templates.

Composite pages

The wikitext of a page may (partly or fully) consist of tags for the inclusion of component pages. The "templates" are not necessarily in the template namespace, and may be more or less self-contained pages by themselves. A disadvantage of putting the components in the template namespace is that the component page may, by itself, be of a nature that it belongs in e.g. the main namespace, while the prefix would suggest otherwise; also the prefix would clutter the pagename.

Examples are:

• m:Help:A simple composite example
• w:Wikipedia:Village pump with six component pages, e.g. w:Wikipedia:Village pump (technical)
• daily a page like w:en:Wikipedia:Votes for deletion/Log/2005 May 31 where each component page consists of the discussion on the deletion of one Wikipedia page, e.g. w:en:Wikipedia:Votes for deletion/Sp3tt (for this day there are 75 of such component pages)
• m:Meta:Translation/Coordination, mainly containing
  • m:Meta:Translation/Coordination/List/Meta
  • m:Meta:Translation/Coordination/List/Main
• [6] - rejection of composite page by w:en

This allows the user the choice between viewing the component pages separately or combinedly. One may want to view a page separately if one has a slow connection; also sometimes people have sentimental reasons for having a separate page about a topic, e.g. a village. Viewing the combined page is much more convenient if there are many small component pages; even if a subbtopic page does not provide additional info, if it exists anyway, and is linked to, it is useful to display the content (making clear that the whole content is shown), it saves the trouble of checking the contents by following the link.

In the latter case the search function of the browser can be used for searching in the combined page. Similar to the section editing feature, it allows editing a component page; however, there is no possibility to have the combined wikitext in the edit box.

Edit history, recent changes, watching pages, and "what links here" work separately for the component pages and the composition page, not for the composite page. Related changes works for the component pages and for the composite page. Page protection can be set for selected component pages and for the composition page, not directly for the composite page.

The talk page of a composition page is used to talk about the composition and the page in general, and could in addition be a composite page of the talk pages of the component pages.

A composite page has an integrated TOC and section numbering; the numbering is not reset for each component page.

Editing a section of a component page can be done directly from the composite page, see editing sections of included templates. After saving, one ends up at the page for the component page to which the section belongs.

On projects with the interlanguage link feature the composite page shows the combined interlanguage links of all component pages, hence possibly multiple links for one language or even for one page.

For easy access to the component pages, links to them on the composite page (for example by self-links on the component pages) are convenient. Alternatively, access is through section editing, or, if the component pages are in the template namespace, through the list of templates called from the composite page, at its edit page.

Conversely, for easy access from a component page to the composite page(s) that call(s) it (if there are not too many of them) it is convenient to link the component page to them (on a composite page one becomes a self-link).

See also w:Wikipedia talk:Template namespace#transcluding prose.

Pages with a common section

A section on the relationship of the subjects A and B, or a subtopic equally relevant for A as for B, can be put both in page A and in page B, by making it a separate page C, called as a template from A and B.

Remarks:

• For readers reading both A and B, it is useful that the duplication be indicated by a message or a special lay-out; otherwise it is confusing and inconvenient. One can for example use template:common section ( talk edit history links ):
  (This section appears in several articles.)
• After saving one ends up viewing the template page. For easy access to the calling pages it is convenient to link the called page to them (on a calling page one becomes a self-link). This may well be integrated in the message about the duplication. It is even more convenient than the two-step link as shown above.
• The section level of the embedded section(s) has to be the same in each embedding page. The same applies to lay-out and style.
• Pages like C can be put in
  • the same namespace as A and B; advantage:
    • the kind of content of C is the same as that of A and B
  • the template namespace; advantages:
    • C appears in the list of templates called from A and B, at their edit pages
    • C by itself may not satisfy the standards for pages in the namespace of A and B, such as providing context (however, the message about the duplication explains it)

Examples:

• Help:Editing sections of included templateshttp://thescubawiki.com/Help:Editing_sections_of_included_templates (talk, backlinks, edit)
• Help:Alphabetic orderhttp://thescubawiki.com/Help:Alphabetic_order (talk, backlinks, edit)

For various remarks which also apply here, see also the previous section.

Repetition within a page

For a succession of similar pieces of content, as in a list, a computer program would use a loop. What comes closest in MediaWiki is putting the loop body in a template, and calling the template repeatedly, usually with a varying parameter value. This is somewhat primitive for a loop:

• instead of "for i=1 to 5" we need to enumerate the values 1, 2, 3, 4, 5; on the other hand, this gives the versatility to use just as easily less regular values such as de, en, fr (collection-controlled loop).
• repetition of code is minimized by the template, but the template call itself has to be repeated each time (but see also the next section)

Example:

• Template:List of Languages - the "loop body" is in Template:Lang def; compared with putting the content of the latter directly in the list the advantage is that the variable part (the value of "code") occurs once each time in the code, although it is used twice. This is important because the fixed part of the list item code can be copied while the variable part is typically inserted manually.

The list of template calls can be in another template, with the name of the called template equal to or depending on a parameter, see e.g. template:Do for every Dutch municipality ( talk edit history links ).

For repetition of the same text the loop body can be a parameter, e.g. Template:X5 (see list).

A double loop is achieved by a second template that repeatedly calls the first. Similarly for a triple loop, etc. See e.g. w:Template:Ld, w:Template:L2d, and w:Template:L3d.

An example where the same template is used for different loop levels is Template:Loop 2. Because the software has a built-in protection against infinite nesting (if there is, there will be an error e.g. Fatal error: Maximum execution time of 30 seconds exceeded in /w/includes/Parser.php on line 775), a redirect is used for each level. The number of levels that the template can handle is determined by the number of parameters specified in the two template calls it comprises (because going up a level requires an extra parameter) and the number of existing redirects.

Similarly Template:Lanlp 1 is used for both the inner and the outer of a double loop. Adding an item (here a language) adds to each row and also adds an extra row.

Providing effective repetition without repetition of similar template calls in the wikitext

A technique for repetition of similar template calls without actually putting this list in the wikitext is demonstrated in template:for ( talk edit history links ), and a more primitive method described below.

Example (using Template:t2demo containing "start-{{{1}}}-middle-{{{2}}}-end<noinclude>[[Category:Demo template]]</noinclude>") (see the master text at m:Help:Template#Repetition_within_a_page, on Wikipedia template "for" is different):

{{for|; |call=t2demo|pc1n=2|pc1v=constant|abc|def|ghi}} gives:

Template:1x; Template:1x; Template:1x

Description of the old template:List of template calls ( talk edit history links ):

For an arbitrary template with up to three nameless parameters, it is equivalent to calling the template repeatedly, with the first parameter varying, and the possible other parameters fixed: one specifies the name, the values of the fixed parameters, and the list of values the first parameter should have in consecutive template calls, with a sequential number each, and ending with "end". The technique requires redirects like Template:List of template calls 3, as many as the maximum number of repetitions.

If e.g. the second parameter varies, or two parameters, then a similar template can be made, but each version requires its own set of redirects.

Example (using Template:t2demo containing "start-{{{1}}}-middle-{{{2}}}-end<noinclude>[[Category:Demo template]]</noinclude>"):

{{List of template calls|t2demo|constant||abc|1|def|2|ghi|end|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||}}

gives:

start-abc-middle-constant-endTemplate loop detected: Template:List of template calls 1

The empty parameters are needed in accordance with the maximum number of parameters the repeated template can have (currently three) and the maximum number of repetitions. Putting more empty parameters than needed at the end does not matter, but the number of empty parameters in the beginning of the list should be correct.

See also Help:Recursive conversion of wikitext.

Ambiguity of a reference to "this page"

If a page is included in another page, a reference to "this page" on the included page is ambiguous. Use noinclude or includeonly tags depending on what is meant. Alternatively, mention the page name explicitly, without using {{PAGENAME}}.

Internal links

In the case of an internal link in a template with the target depending on a parameter, and in the case of a link with the target depending on a template, existence detection works as usual.

Examples:

• {{tli|insert in target|insert in label}} (using Template:tli containing "[[:Template:Tli]]") gives Template:Tli
• [[a{{tciit}}b|c{{tciil}}d]] (using Template:tciit containing "[[:Template:Tciit]]" and Template:tciil containing "[[:Template:Tciil]]") gives [[aTemplate:Tciitb|cTemplate:Tciild]]

• {{tli|insert also in target|insert in label}} (using Template:tli) gives Template:Tli (for the demo this page is supposed to be non-existing)
• [[a{{tciit}}e|c{{tciil}}d]] (using Template:tciit and Template:tciil) gives [[aTemplate:Tciite|cTemplate:Tciild]] (for the demo this page is supposed to be non-existing)

• {{la|Help:Tabl|tabl}} (using Template:la containing "[[:Template:La]]") gives: Template:La

• Template:Pvn

Templates and external links

Examples:

• {{tle|insert in target|insert in label}} (using Template:tle containing "[http://a{{{1}}}b c{{{2}}}d]")} gives in targetb cinsert in labeld
• {{tle2|insert in target}} (using Template:tle2 containing "http://a{{{1}}}b")} gives "http://ainsert in targetb"; note that brackets separated from the http:// are not recognized as belonging together:
  • [{{tle2|insert in target}} label] gives in targetb label
  • [{{tle2|insert in target}}] gives in targetb
• {{tle3|insert in target}} (using Template:tle3 containing "[http://a{{{1}}}b]")} gives in targetb
• [http://a{{tciit}}b c{{tciil}}d] gives Template:Tciitb cTemplate:Tciild
• http://a{{tciit}}b gives "http://aTemplate:Tciitb"
• [http://a{{tciit}}b] gives Template:Tciitb

However, a URL can not be composed of:

• a first part in a parameter and a second part added by the template (although we have seen above that reversed it works: a second part in a parameter and a first part prefixed by the template)
• a first part in a template and a second part after the template (although we have seen above that reversed it works: the second part in a template and the first part before the template)

Example of first restriction:

• {{tae|http://www.}} (using Template:tae containing "{{{1}}}add at the end")} gives http://www.add at the end

Examples of second restriction:

• [{{th}}add_at_the_end] (using Template:th containing "http://www.")} gives [7]
• "{{th}}add_at_the_end" gives "http://www.add_at_the_end"

Noinclude, includeonly, and onlyinclude

This feature is not available before version 1.6. These features are applied as nesting pairs, or 'Blocks', as it is said they enclose the material so that they can be said to begin and end a block of wikitext (code).

noinclude blocks

Anything between <noinclude> and </noinclude> will be processed and displayed only when the page is being viewed directly; it will not be included or substituted. Possible applications are:

1. Categorising templates, see template documentation.
2. Interlanguage links to similar templates in other languages.
3. Pages in the MediaWiki namespace.

includeonly blocks

The converse is <includeonly>. Text between <includeonly> and </includeonly> will be processed and displayed only when the page is being included. Applications include:

1. Adding all pages containing a given template to a category, but not the template itself.
2. Avoiding messy rendering on the template page, e.g. "{{#expr:{{{1}}}}}" gives "Expression error: Unrecognised punctuation character "{"" [8].

Note that spaces and newlines between the general content and the tagged part belong to the general content. If they are not desired the include tag should directly follow the content on the same line:

<noinclude>this is </noinclude>fine<includeonly>, closing tags are
</includeonly><noinclude>
less critical, but must be specified.</noinclude>

nesting

Nesting an includeonly block within a noinclude block (or vice-versa) is legal but pointless.

onlyinclude blocks

With <onlyinclude>wikitext</onlyinclude> on a page, the display of the wikitext so surrounded and the rest of the page (except includeonly parts) is rendered on the page itself normally (note: this means interwiki translation links will behave as normal external links, unless they are further bracketed by <includeonly>). The demo page below holds a full screenful of text and code, including several includeonly blocks as well as a single onlyinclude block as a demonstration. It is advisable to look at that page in edit mode.

However, in transclusion, the page gives only the parts within onlyinclude blocks. Using the test line:

Using [[Help:Template/onlyinclude demo]], 
     <nowiki>{{Help:Template/onlyinclude demo}}</nowiki> 
          gives '''{{Help:Template/onlyinclude demo}}'''. 

When repeated below we get: Using Help:Template/onlyinclude demo, {{Help:Template/onlyinclude demo}} gives def. When that page is included, it does not even transclude other blocks which are defined as includeonly parts, unless such are also within the onlyinclude block. So on a page with onlyinclude tags, text within includeonly tags is never rendered, i.e., it is reduced to wikitext comment. See also Help:Template/onlyinclude demo 2 and its talk page.

Caveats on splitting and interworkings

Attempts to nest split pairs of these tags, or the similar <nowiki> and </nowiki> pair, won't work as expected.

If say <nowiki> begins within the general page content, or in a "noinclude" part, or in an "includeonly" part, then it also has to be closed within the same part.

The code ~<includeonly>~</includeonly>~~ will be displayed as ~~~ when the template is not included, ~~~~ when the template is included, but it will only be expanded as the active user when the template is subst'd, which is to say when it has been joined within the same block once again.

Wiki markup at the beginning of a template

If the first included character of a template is one of the Wiki markup characters :;*#, then it's interpreted as being at the beginning of the line (even when the template call is not).

To avoid this effect use <nowiki>#</nowiki> or a numeric character reference (NCR) or HTML entity like say &#58; for a colon. This NCR is also useful in conjunction with definition lists.

Substitution

Main article: Help:Substitution

Putting "subst:" after the double opening braces causes an automatic conversion of wikitext when the referring page is saved: the subst tag is replaced by the wikitext of the template, with the parameter values substituted for the parameters.

For optional multi-level substitution of templates add a substitution parameter with the empty string as default, e.g. {{{substp|}}}, after the opening braces in all calls of templates, parser functions and variables in templates, and add parameter definitions of the form "substq={{{substr|}}}" in all template calls within templates. Note that the use of multiple substitution parameters allows selective substitution. Maximum flexibility is obtained by making them all different. Sometimes a little less flexibility is needed; e.g. there may be a group of parser functions in a template for which it is sufficient to be able to choose between substitution of all or none in the group.

To reduce, in the wikitext, undefined parameters with default to the defaults themselves, use the alternative way of specifying a parameter default.

Redirection

When a page called for inclusion is a redirect page, the redirect target is included instead. As usual, a double redirect or broken redirect does not work.

A page that consists of nothing else than the inclusion of another page as a template, shows similarities to a redirect to that other page, but also many differences, including:

• the result has as header the name of the referring page
• there is no redirect message
• the buttons such as edit (for editing the whole page), watch, talk, history, "what links here", and "last modified", etc., refer to the referring page (to go to the target page, a section edit link can be used, from there the whole page can be accessed)
• the referring page is in the same categories as the target page, except when includeonly and/or noinclude tags are used
• "double redirects", with one or both being this kind of "pseudo-redirect", work.

Compare Help:Template namespace with Help:Template namespace - demo of alternative for redirect.

In a page that in turn includes such a referring page there is no difference.

Note that embedding works for all pages where redirecting works, and it also fails for all pages where a redirect won't work.

Self-transclusion

A page can transclude itself, but is protected against an infinite loop: the transclusion in the transcluded copy of the template is replaced by the bolded pagename. See Help:Self-transclusion demohttp://thescubawiki.com/Help:Self-transclusion_demo (talk, backlinks, edit) and Help:Self-transclusion demo 2http://thescubawiki.com/Help:Self-transclusion_demo_2 (talk, backlinks, edit).

Transcluding on page A page B redirecting to page A allows more repetition, see Help:Self-transclusion demo with redirecthttp://thescubawiki.com/Help:Self-transclusion_demo_with_redirect (talk, backlinks, edit) with Help:Self-transclusion demo redirecthttp://thescubawiki.com/Help:Self-transclusion_demo_redirect (talk, backlinks, edit).

If due to the use of braces hidden in a template (see Help:Recursive conversion of wikitext) the saved wikitext of a page contains a substitution call to itself, then on the next save the substitution is applied for one level; the transclusion in the transcluded copy of the template is replaced by a link to the pagename. Thus it becomes a self link, i.e., it becomes bolded text with immediately following characters also bolded. This time the link is followed in the wikitext by the hidden message "<!-- WARNING: template loop detected -->"; see [9]; this edit was automatic by edit/save without making a change in the wikitext oneself.

Parsing braces

If some braces are "hidden" in a template, as in template:lb ( talk edit history links ), then parsing of pairs of double and triple braces is based on visible braces only. In the case of partial substitution, first parsing is done for the purpose of substitution, then parsing is done again for rendering:

• {{t1|{{lb}}tc}}}} gives start-{{tc-end}} - the last-but-one pair of closing braces is taken as closing braces of template:t1 ( talk edit history links )
• {{t1|{{subst:lb}}tc}}}} gives the wikitext {{t1|{{tc}}}} rendered as start-in-end - after substitution the last pair of closing braces is taken as closing braces of t1
• {{subst:t1|{{subst:lb}}tc}}}} gives the wikitext start{{tcend}} rendered as startTemplate:Tcend - the last-but-one pair of closing braces is taken as closing braces of t1 for both substitutions
• {{subst:subst}}t1|a}}, substituting template:subst ( talk edit history links ), gives the wikitext {{subst:t1|a}} rendered the same; in the next edit the wikitext is converted to "startaend".
• {{subst:tsubst 1|a}}, substituting template:tsubst 1 ( talk edit history links ): ditto.

With parser function #if instead of template:t1:

• {{#if:x|{{lb}}t1|a}}|b}} gives {{t1|b}} - the last-but-one pair of closing braces is taken as closing braces of #if.
• {{#if:x|{{subst:lb}}t1|a}}|b}} gives the wikitext {{#if:x|{{t1|a}}|b}} rendered as start-a-end - after substitution the last pair of closing braces is taken as closing braces of #if.
• {{subst:#if:x|{{subst:lb}}t1|a}}|b}} gives the wikitext {{t1|b}} rendered as start-b-end - the last-but-one pair of closing braces is taken as closing braces of #if for both substitutions.
• {{subst:#if:x|{{subst:subst}}t1|a}}|b}} gives the wikitext "{{subst:t1|b}}" rendered the same: "{{subst:t1|b}}" (the substitution phase is finished; the ordinary template expansion phase ignores substitution calls); in the next edit the wikitext is converted to "startbend".
• {{subst:#if:x|{{subst:#if:x|{{subst:subst}}t1|a}}|b}}|c}} gives the wikitext "{{subst:t1|c}}" rendered the same: "{{subst:t1|c}}".
• {{subst:#if:x|{{subst:tsubst 1|a}}|b}} gives the wikitext "startaend". Apparently there is a substitution phase of parameter expansion resulting in the parameter value "{{subst:t1|a}}", and another substitution phase for the substitution of #if, taking the parameter value not as plain text, but interpreting the "subst:" in it again.

See also Help:Recursive conversion of wikitext.

Comparison of linking and embedding

Linking and embedding have in common:

• if the page does not exist, a link to the edit page is shown; the links are identical if it is not a piped link; the link does not show parameters and does not show whether, after creation, the new page will be linked or embedded.
• the name can depend on variables and parameters

Predefined templates

Variables and parser functions can be considered predefined templates. They do not have a page that defines in terms of wikitext what they do, because their action is something extra that cannot be constructed from more basic wikitext functionality.

Some additional differences:

• Parser functions use ":" instead of the first "|".
• An edit page does not list predefined templates used on the page.
• No "What links here" is available for predefined templates, to find the pages where they are used.
• Apart from #switch, predefined templates don't allow you to define named parameters, and therefore equal signs generally have no special effect, comparison:

  {{ #if: not blank | 2=abc }} gives 2=abc

  {{ ifdef | not blank | 2=abc }} gives abc

Ordinary and predefined templates have in common that their parameter values can depend on ordinary and predefined templates. In the case of named parameters, the names used in the template call can also depend on ordinary and predefined templates. This applies also for the named parameters of #switch.

Template expansion

Expansion of wikitext can be relevant even if the wikitext resulting from these subevaluations cannot have effect on the overall wikitext, because the expansion can have side effects:

• Subevaluations producing links add on the target page to the list of incoming links (What links here), based on the pagelinks table, even if there is no link on the resulting page.
• Subevaluations involving template calls add on the template page in "What links here" and on the edit page of the page concerned to inclusion items, based on the templatelinks table.
• Some extensions may perform some action during a subevaluation, e.g. with VariablesExtension a subevaluation may involve assignment of a value to a variable.

In the case of #ifexpr etc., either the then-part or the else-part is expanded, not both. Also the wikitext for the value of an unused template parameter is not expanded.

See also ParserFunctions#Code_execution.

Templates as table pieces

Tables using wikitable syntax can have pieces in templates. Tables using HTML syntax can not, by default. Thus, if you have a table row like

 |1||2
 |-

in a template called "Row1" and a table row like

 <tr><td>1</td><td>2</td></tr>

in a template called "Row2", and you have tables like

 
  {| border="1"
  |a||b
  |-
  {{Row1}}
  |c||d
  |}
  

and

 
  <table border="1">
  <tr><td>a</td><td>b</td></tr>
  {{Row2}}
  <tr><td>c</td><td>d</td></tr>
  </table>
  

You will obtain:

and

But if you set the variable $wgUseTidy HTML table will work too. It's false by default, but it is true in most Wikimedia projects.

See also conditional table row.

Templates in different versions of MediaWiki

Version 1.6

• More magic words and the parameter default mechanism were added.
• <noinclude> and <includeonly> (see above) were added.

Version 1.5

• More magic words were added.

Version 1.4

• Including the same template more than five times in the same page works from version 1.4, now on all Wikimedia sites. Also new was that subst can be used with parameters.

Version 1.3

• See, among other things, default values of parameters. Starting with version 1.3 the prefix "msg:" is generally optional.

Version 1.2.6

• In MediaWiki version 1.2.6, make a page MediaWiki:mytemplate and refer to it with {{msg:mytemplate}}. In this version parameters are not possible.
• Compatibility with 1.3, in the sense of having the content in Template:mytemplate, is possible with a redirect from MediaWiki:mytemplate to Template:mytemplate on the 1.2.6 project.

History

When ParserFunctions were not available yet, multiple assignments of parameters with the same name (and thus allowing parameter overrides) were ingeniously used to perform branching, e.g. in the now deleted en:Template:If defined.

Revision history of pages containing templates

Pages in the stored page history consist of wikitext with possible references to templates and images. When viewing an old version of a page, these refer to the current versions of the templates and images, if these still exist. Thus the former composite page is not reconstructed.

Other pages not primarily meant for direct viewing

Pages not primarily meant for direct viewing include, apart from templates:

• multilingual portal pages, see www
• CSS and JS pages, see Help:User style
• pages in the MediaWiki namespace, see Help:System message
• w:Wikipedia:Book sources, used by w:Special:Booksources
• m:Spam blacklist

Notes

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See also

• Help:Advanced templates
• Introductions:
  • Transclusionhttp://thescubawiki.com/Transclusion
  • Help:A quick guide to templateshttp://thescubawiki.com/Help:A_quick_guide_to_templates
  • mw:Help:Templates
• Help:Calculation
• Help:Parser function
• Help:ParserFunctionshttp://thescubawiki.com/Help:ParserFunctions
• Help:Parameter default
• Help:Magic words
• Help:Substitution
• Help:Template documentation
• Help:Variable
• Help:What links here
• Special:Mostlinkedtemplates - shows the number of pages in which each template is transcluded, not counting transclusions through redirects
• Special:Unusedtemplates - templates which are not transcluded (however, they may be used for substitution)
• interwiki transclusion
• MediaWiki help templates
• List of all templates on this server
• Templates of Wikimedia projectshttp://thescubawiki.com/Templates_of_Wikimedia_projects
• w:Wikipedia:Template namespacehttp://en.wikipedia.org/wiki/Wikipedia:Template namespace
• mw:Extension:ExpandTemplates
• mw:Extension:Labeled Section Transclusion - transclusion of part of a page
• w:Wikipedia:Template doc page patternhttp://en.wikipedia.org/wiki/Wikipedia:Template doc page pattern
• w:Wikipedia:Template_limitshttp://en.wikipedia.org/wiki/Wikipedia:Template_limits
• DynamicFunctions##arg:http://thescubawiki.com/DynamicFunctions#.23arg: - instead of including a page for given parameter values, this allows linking to a page for given parameter values. Syntax for parameter use: {{arg:parameter name|default}}. Syntax for linking: external link style with "&parameter name=parameter value" added to the URL.
• w:Wikipedia:Anatomy_of_a_templatehttp://en.wikipedia.org/wiki/Wikipedia:Anatomy_of_a_template
• w:Wikipedia:Transclusion_costs_and_benefitshttp://en.wikipedia.org/wiki/Wikipedia:Transclusion_costs_and_benefits
• mw:Manual:Parser.phphttp://www.mediawiki.org/Manual:Parser.php

See also Meta:List of templates.

Links to other help pages

Help contents

Meta | Wikinews | Wikipedia | Wikiquote | Wiktionary | commons: | mw: | b: | s: | mw:Manual | google

Versions of this help page (for other languages see below)

Meta | Wikinews | Wikipediahttp://en.wikipedia.org/Help:Template | Wikiquote | Wiktionary

What links here on Meta or from Meta | Wikipedia | MediaWiki

Reading

Go | Search | Stop words | URL | Namespace | Page name | Section

Backlinks | Link | Piped link | Interwiki link | Redirect | Category | Image page

Logging in and preferences

Logging in | Preferences | User style

Editing

Advanced editing | Editing FAQ | Edit toolbar | Export | Import | Shortcuts

Tracking changes

Recent changes (enhanced) | Related changes | Watching pages | Diff

Page history | Edit summary | User contributions | Minor edit | Patrolled edit

Style & formatting

Wikitext examples | Reference card | HTML in wikitext | List | Table | Sorting | Colors

Special input and output

Inputbox | Special characters | Displaying a formula | Images (uploads) | EasyTimeline

Advanced functioning

Template | Advanced templates | Parser function | ParserFunctions | Parameter default

Variable | Magic word | System message | Substitution | Array | Calculation

Page management

Starting a new page | Renaming (moving) a page | Protecting pages | Deleting a page

Special pages

Talk page | Testing | Sandbox | CentralNotice

Template:-