Help:Templates

If you have standard texts you want to include on several pages, the MediaWiki template feature comes into play.

Creation
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 " ", assigning it to that namespace; besides this, you can create them like any other wiki page.

The simplest use of templates is as follows. 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. Such inclusion on a page is called transclusion in MediaWiki.

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.

Usage
Templates can be used in other pages in these ways:


 * , described above, 'transcludes' (i.e. includes a copy of) the content of the template (stored in the page Template:Name ) whenever the page containing the template transclusion is fetched and displayed; i.e. if the template is later changed, the displayed transcluding page will automatically change too
 * substitutes that string with plain text from the template as if it were copied and pasted in from the template by hand
 * was introduced in rev:61710 to allow for substitution that does not break transclusion, see wikipedia:Help:Substitution.
 * includes the template in a form that displays it as raw wiki syntax (the way  does) when the page containing it is fetched.

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


 * includes
 * includes
 * includes
 * replaces itself with the contents of

If no such namespace exists, the full title is assumed to be a template:


 * includes

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. 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 char. MediaWiki allows parameters to be passed to the template in three ways.

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

In this case, template  receives parameters   and   and produces:

Inverting the order of the parameters:

causes template  to receive parameters   and   and inverts the result:

So, the order in which anonymous parameters are passed in is crucial to its behaviour.

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:

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:

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:

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:

Control template inclusion
You can control template inclusion by the use of  and tags.

Anything between  and   will be processed and displayed only when the template's page is being viewed directly.

Possible applications are:
 * Categorising templates
 * Interlanguage links to similar templates in other languages
 * Explanatory text about how to use the template

The converse is. Text between  and   will be processed and displayed only when the page is being included. The obvious application is to add all pages containing a given template to a category, without putting the template itself into that category.

Note: when you change the categories applied by a template, the categorization of the pages that use that template may not be updated until some time later: this is handled by job queue.

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.

Users can also look in Category:Templates as long as the template has been categorized. Users can check Special:UncategorizedTemplates if they can not find their template in Category:Templates.

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

Usage
Welcome users:

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

Recommended form of templates
Usually, the Scratch 2.0-style header styling is used. See the template for more info.

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:

If you have import rights on the new wiki

 * 1) Go to Special:Export on the original wiki. Enter the name of the template in the big text box, check "Include templates" and click Export. This will download a .xml file.
 * 2) Go to Special:Import on the new wiki and upload the .xml file.
 * 3) Look for CSS classes (like class="foobar") 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.
 * 4) If the template uses ParserFunctions, you have to install the ParserFunctions extension.

If you do not have import rights on the new wiki

 * 1) Copy the template text to the new wiki; link to the original page in the edit summary for attribution.
 * 2) Edit the template on the new wiki, and look through the list of templates at the bottom. The ones in red will also need to be copied from the original wiki to the new wiki. You may have to repeat this process multiple times before all dependency templates have been recognized and copied.
 * 3) Look for CSS classes (like class="foobar") 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.
 * 4) If the template uses ParserFunctions, you must install the ParserFunctions extension.