Help:Template: Difference between revisions

{{Wikipedia how to|H:T|WP:TEMPLATE}}

A '''template''' is a Bharatpedia page created to be included in other pages. Templates usually contain repetitive material that might need to show up on any number of articles or pages. They are commonly used for [[Bharatpedia:Glossary#Boilerplate text|boilerplate]] messages, standardized warnings or notices, [[Help:Infobox|infoboxes]], [[WP:Navbox|navigational boxes]], and similar purposes.

The most common method of inclusion is called [[Bharatpedia:Transclusion|transclusion]], where the [[WP:wikitext|wikitext]] of the target page contains a reference to the template, using the {{tnull|{{var|Template name}}}} syntax. Another method is [[Help:Substitution|substitution]], where the content of the template is copied into the wikitext of the target page, just once, when it is saved.

[[File:Introduction to templates on Wikipedia.webm|thumb|A basic overview of how templates work (8-minute video)]]

Most templates are pages in the [[WP:Template namespace|Template namespace]], which means that they have titles in the form "Template:{{var|XXXX}}". It is possible, however, to transclude and substitute from any namespace,{{efn|Namespaces from which transclusion is not allowed are specified on a wiki by the variable <code>[[mw:Manual:$wgNonincludableNamespaces|$wgNonincludableNamespaces]]</code>.}} and so some template pages are placed in other namespaces, such as the [[WP:User namespace|User namespace]]. Template pages have associated [[WP:talk page|talk pages]].

Templates can contain any desired [[WP:Wikitext|wikitext]], including calls to other templates. They have some limited programming capacities: customizable values (called [[#Parameters|parameters]]); calculation and branchings (using [[Help:Parser functions|parser functions]]); and access to wiki-specific variables ([[Help:Magic words|magic words]]), such as dates, times, and page names. They may also contain [[HTML element|tags]] which define which parts of the wikitext are to be included when the template is transcluded or substituted. This means that the appearance of the template page itself need not be the same as that of the transcluded content (for example, it can contain documentation, categories, etc. for the template).

The prefix <code>Template:</code> before the template name is the default one and need not be included. However, for templates stored in other namespaces, the prefix, such as <code>User:</code>, must be specified. To transclude a page in [[WP:mainspace#Namespace|mainspace]], precede its title with a colon, as <code>{<nowiki />{:{{var|Page name}}}}</code>.

{{A note}} Attempting to transclude a template that does not exist produces a [[WP:Redlink|red link]], just like linking to any other nonexistent page. Following the link allows one to create that particular template. It is not possible to transclude pages between projects (such as different-language Bharatpedias or MediaWiki)—to use a template on another language project, a copy of the template must be created in that project.

{{shortcut|H:PARAMETER|WP:PARAMETER}}

Parameters can be specified (and will do nothing) even if not represented in the template's code. For example, {{para|reason}} is frequently used as a pseudo-parameter to explain briefly in the wikisource why the template was placed.{{efn|Some templates, such as {{tlx|Requested move}}, have code to display {{para|reason}} as visible output; whether to do so is determined on a template-by-template basis.}} Some templates call [[Module:Check for unknown parameters]] to warn the editor if a parameter is being used that is not accounted for in the template's code; this is mostly used for [[WP:Infobox|infoboxes]] and other templates with a large number of complicated parameters, where the presence of an unknown one is usually an unintentional error. If you update such a template to include a new parameter, its call to the module must also be updated to include the new parameter.

Whereas MediaWiki variable names are all uppercase, template names have the same basic features and [[WP:NCHASHTAG|limitations]] as all [[Help:Page name|page names]]: they are case-sensitive (except for the first character); underscores are [[parsed]] as spaces; and they cannot contain any of these characters: <code><nowiki># < > [ ] | { }</nowiki></code>. This is because those are reserved for [[wiki markup]] and [[HTML]].

The [[number sign]] <code>#</code> is called a [[fragment identifier]] because it denotes a {{em|fragment}} or section of a document (such as a [[Help:Section|section]] in a Bharatpedia article). Although it [[WP:ANCHOR|can be used]] to link to a section of a template page (like [[Template:Portal#Example]]), there is no reason to put a fragment identifier or fragment name in a template reference. In {{tnull|Portal{{var|#Location}}|Books}}, for example, the string <code>{{var|#Location}}</code> has no purpose and is thus ignored.

When a template is substituted, its content is [[hard-coded]] in the page rather than [[WP:Transclusion|transcluded]]. To learn how and [[Help:Substitution#When to use substitution|when]] to substitute a template, see [[Help:Substitution]].

* If you want the template to leave a [[WP:~|time stamp or signature]], you can write <code>&lt;noinclude>&lt;nowiki>&lt;/noinclude><nowiki>~~~~~</nowiki>&lt;noinclude>&lt;/nowiki>&lt;/noinclude></code>, but this will only work if you substitute the template. If you transclude it, you'll just get <nowiki>~~~~~</nowiki>.

Templates are created and edited in much the same way as any other page: choose an appropriate name, navigate to that page, then click the "Edit" tab or create a new page as needed. As mentioned above, templates are normally placed in the [[WP:Template namespace|Template namespace]], though templates intended for your own personal use or for experimentation can be created in your own [[WP:user space|user space]]. Anything that can be included on a normal page or article can be included on a template, including other templates (called ''{{dfn|subtemplates}}''). Templates often make use of programming features—parameters, parser functions, and other [[Help:Magic words|magic words]]—which allow the transcluded content to vary depending on context. There are also special tags to control which information is transcluded and which is not.

Before creating a template, do a quick search for existing templates (such as by exploring [[:Category:Wikipedia templates]]) to see if there is already a template that does what you want or a similar template whose code can be copied and modified (or left in place and expanded). Look for generic templates on which the new template can be based; for example, [[WP:Navbox|navbox]] templates can be easily created by calling the generic [[Template:Navbox]].

There is no hard rule about what name to choose for a template—make it short but reasonably descriptive. If similar templates exist, try to follow a consistent naming pattern. Templates can be renamed without breaking existing [[Bharatpedia:Transclusion|transclusions]] (what is called '''breakage'''), provided a [[WP:Redirect|redirect]] to the new template name is left behind.

Be extremely careful when editing existing templates—changes made can affect a large number of pages, often in ways you might not expect. For this reason many high-use templates are [[WP:Protection|protected]] against editing except by [[WP:Administrator|administrators]] and [[WP:Template editor|template editors]]; other editors can propose changes on the talk page. Some templates offer a sandbox and [[Bharatpedia:Template test cases|test cases]] for experimentation.

To propose the deletion or merger of unused or inappropriate templates or templates that can easily be merged, go to [[WP:Templates for discussion|Templates for discussion]] (TfD).

because the parameter is not expanded. Instead, you can use the <code><nowiki>{{#tag:}}</nowiki></code> [[WP:PF|parser function]], which is—for example—used in {{tlx|sfn}} to generate the {{tag|ref}} element; see also [[Help:Magic words#Formatting|Help:Magic words § Formatting]]. Therefore, the following example will work:

{{shortcut|WP:NEST}}

{{shortcut|WP:TEMPLATE LOOP}}

{{shortcut|WP:NOINCLUDE|WP:INCLUDEONLY|WP:ONLYINCLUDE}}

By default, when a template is [[Bharatpedia:Transclusion|transcluded]] (or [[Bharatpedia:Substitution|substituted]]), the entire wikitext (code) of the template page gets included in that of the target page. However, it is possible to modify that behaviour, using tags that specify which parts of the template code are to be included. This makes it possible to avoid transcluding information intended for display only on the template page itself, such as the template's {{tl|documentation}}, [[WP:Category|categories]], and [[WP:Interwiki links|interwiki links]]. It is also possible to have parts of the code be transcluded, but {{em|not}} be processed on the template page itself (e.g., categories to be applied to the target pages which do not apply to the template). The tags are as follows:

* If the first character produced by a template or [[WP:PF|parser function]] is one of four wiki markup characters—<code>:</code>, <code>;</code>, <code>*</code>, <code>#</code>{{efn|These are defined in the [https://web.archive.org/web/20180625163321/https://doc.wikimedia.org/mediawiki-core/master/php/classParser.html#ad463888e40c078ac9bcfcaf1231e39d7 <code>doBlockLevels</code> function of Parser.php].}}—then it is processed as though it were at the beginning of a line, even when the template tag is not. This allows the creation of various kinds of lists in templates where the template may not always be in the correct place for a list. To avoid this, either use {{xtag|nowiki|s}} before the markup or use the [[HTML]] entities <code>&amp;#58;</code>, <code>&amp;#59;</code>, <code>&amp;#42;</code>, and <code>&amp;#35;</code> respectively. In some cases, the HTML entities will work when the {{tag|nowiki|s}} does not. The problem often occurs when a parameter value in a template call starts with one of the four characters.

* To protect server resources and avoid infinite loops, the parser imposes certain limits on the depth transclusion nesting and on the page size with expanded templates. This may cause pages to break when using very complex templates, particularly if there are multiple such templates on the same page. For more information, see [[Bharatpedia:Template limits]]. A page's overall load on the server can be checked by examining the generated HTML for a page and looking for the <code>NewPP limit report</code> comments.

In the case of complex templates, the documentation (together with categories) is often kept on a separate [[WP:Subpage|subpage]] of the template page (named "Template:{{var|XXX}}/doc"). This also applies to many [[WP:Protection|protected]] templates, which allows the information to be edited by non-administrators. This is achieved by placing the {{tlx|Documentation}} template after the main template code and within {{tag|noinclude}} tags. If the "/doc" subpage does not exist, a link will then appear enabling it to be created.

Some templates contain category definitions in their transcluded code, since they are intended to place the target pages in particular categories. This is often done with maintenance categories (placing articles into ordinary content categories in this way is discouraged). When doing this, it may be necessary to use {{tag|includeonly}} tags to keep the template itself out of the category. While developing, testing, sandboxing, or demonstrating a template intended to apply a category, either temporarily replace each category with a test category (starting with [[:Category:X1|X1]], [[:Category:X2|X2]], or [[:Category:X3|X3]]) or suppress categorization (see [[WP:CATSUP|category suppression in templates]]).

Aliases can be created with [[WP:Redirect|redirects]]. For example, [[Template:Tsh]] redirects to [[Template:Template shortcut]]. You can then write {{tlx|tsh|{{var|foo}}}} instead of {{tlx|Template shortcut|{{var|foo}}}}.

'''"Post-expand include size" limit.''' When templates are rendered or expanded to HTML for viewing in your browser, they use memory. This is called the "post-expand include size" and has a limit of 2,048,000&nbsp;bytes. This size is included as an invisible comment in the HTML output—use your browser's view source feature to show the raw HTML and search for "newpp". The report will look like:

NewPP limit report

{{Wikipedia template messages|state=collapsed}}

{{Wikipedia technical help|collapsed}}

[[Category:Wikipedia how-to]]

[[Category:Wikipedia template help]]