Writing templates

Writing templates is much like writing any other wiki page, and the simplest templates really aren't anything more than a typical wiki page that just gets shown on other pages. But most templates use parameters, magic words, and parser functions such as those provided by the standard ParserFunctions (installed by default on all Gamepedia wikis) to make them even more useful.

Writing a simple template
If you create a page called "Template:Welcome" with contents:

Hello! Welcome to the wiki.

you'll have created your first template! If you then insert the code:

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

You can then insert  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.

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:

The thank you note will have a reason (in this case, "all your effort") and a signature ("Me"). Your objective is that any user is 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. hugs,

Notice the use of  and. This is the way to identify, within templates, the parameters that will be passed in when the template is used. 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, or named.

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

In this case, the  template receives parameters   and , 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:

would produce this result:

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

Note: identifying parameters by order (with, etc) works only with anonymous parameters. If your page identifies any parameter by number or name, as shown below, this method will no longer be available to the template which receives them.

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

This time, template  receives parameters   and , though they have been supplied in inverse order, and produces:

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

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. hugs,

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

In this case, template  receives parameters   and   and produces:

A little thank you... for being who you are. 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.

Default values
If you transclude a template that expects parameters, but do not provide them, in this way:

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

A little thank you... for. hugs,

Since no parameters 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. hugs,

then  defines that if no parameter   is provided, then the value   will be used. Similarly,, defaults parameter   to value. Now, transcluding the template again without passing any parameter, results in the following:

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

Control template inclusion
By default, a template's content is displayed in its entirety, both when viewed directly and when included in another page. However, you can control which parts of a template will be seen and included by the use of the,  , and   tags.

Showing content only on the template page
Anything between  and   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
 * Documentation about how to use the template

Alternatively, anything outside  and   is seen only when the template's page is viewed directly. and  have the same purpose, but function in opposite ways.

Showing content only on transclusion or substitution
is not to be confused with, which has a different purpose. Anything between  and   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 (known as a null edit).
 * 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.

Always showing content
Unless  tags are used, everything outside   and   tags 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.

Otherwise, anything inside  tags will be shown both on the template page and when included, unless   tags are used within.

Controlling inclusion based on namespace
Many templates auto-categorize pages and this is very useful. What is not useful is having the template itself in those categories. To avoid this, use the following code:

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.

Templates should always be categorized. Generally, there should be a top level category "Category:Templates" from which editors can browse for templates.

Writing documentation
All templates should have documentation describing how to use them. To add documentation, on the template page add  or   (depending on the wiki).

The documentation should then be written at the "/doc" subpage of the template, for example "Template:Thankyou/doc". Depending on the wiki's template names, the documentation will be written by wrapping the entire page in start and end templates ( and   for example).

Generally, the documentation should include a brief description of the template, the list of parameters used for the template, usage examples, and a list of any other relevant templates in a "see also" section.

Some wikis have different rules regarding documentation, so be sure to read any relevant wiki-specific guidelines.

Copying from one wiki to another
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 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:
 * 2) * 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.
 * 3) * Check the box "Include templates".
 * 4) * Uncheck the box "Include only the current revision".
 * 5) * Click Export.
 * 6) 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 Special:Export on the original wiki, and download an .xml file with the latest version only of all necessary templates, as follows:
 * 2) * Enter the name of the template in the big text box.
 * 3) * Check the box "Include templates".
 * 4) * Check the box "Include only the current revision".
 * 5) * Click Export.
 * 6) * Open the file in a text editor and replace certain XML entities with the corresponding characters: &amp;lt; → <, &amp;gt; → >, &amp;quot; → " and &amp;amp; → &. Because of XML syntax rules, these entities appear in the XML file, but they should not appear in the edit box of the MediaWiki instance.
 * 7) * Manually copy the text inside the  tag of each listed template into a similarly named template in your wiki. In the edit summary of each template, link to the original page for attribution.

This will copy the entire code necessary, and will suffice for some templates.

Extensions
An extension often used in templates is ParserFunctions. Visit page ParserFunctions and check if any of the functions listed there are used in the templates you've copied. The ParserFunctions extension is installed by default on Gamepedia wikis.

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 priviledges, because you'll be editing system messages in the "MediaWiki:" namespace.


 * 1) Look for the use of CSS classes (text like  ) in the template text. If those classes appear in "MediaWiki:Common.css" or "MediaWiki:Monobook.css" on the original wiki, copy them 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 first browsing the code to identify and select the parts that are relevant. You may find comments that can serve as clues to identify the functionality of each part.