Editing Help:Templates (section)

==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 [[Help:Talk pages|talk page]] of other users, such as:

{{Thankyou|all your effort|Me}}
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:

<pre><nowiki>'''A little thank you...'''
for {{{1}}}.
hugs, {{{2}}}</nowiki></pre>

Notice the use of <code><nowiki>{{{1}}}</nowiki></code> and <code><nowiki>{{{2}}}</nowiki></code>. 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: <code><nowiki>{{{ }}}</nowiki></code>. 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 (<code>|</code>). 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:

 <nowiki>{{Thankyou|all your effort|Me}}</nowiki>
In this case, template <code><nowiki>{{Thankyou}}</nowiki></code> receives parameters <code><nowiki>{{{1}}}=all your effort</nowiki></code> and <code><nowiki>{{{2}}}=Me</nowiki></code> and produces:

{{Thankyou|all your effort|Me}}

Inverting the order of the parameters:

 <nowiki>{{Thankyou|Me|all your effort}}</nowiki>

causes template <code><nowiki>{{Thankyou}}</nowiki></code> to receive parameters <code><nowiki>{{{1}}}=Me</nowiki></code> and <code><nowiki>{{{2}}}=all your effort</nowiki></code> and inverts the result:

{{Thankyou|Me|all your effort}}
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:

 <nowiki>{{Thankyou|2=Me|1=your friendship}}</nowiki>

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

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

<pre><nowiki>'''A little thank you...'''
for {{{reason}}}.
hugs, {{{signature}}}</nowiki></pre>

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

 <nowiki>{{Thankyou|signature=Me|reason=being who you are}}</nowiki>

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

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

 <nowiki>{{Thankyou}}</nowiki>

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

{{Thankyou}}
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:

<pre><nowiki>'''A little thank you...'''
for {{{reason|everything}}}.
hugs, {{{signature|Me}}}</nowiki></pre>

then <code><nowiki>{{{reason|everything}}}</nowiki></code> defines that if no parameter <code>{{{reason}}}</code> is provided, then the value <code>everything</code> will be used. Similarly, <code><nowiki>{{{signature|Me}}}</nowiki></code>, defaults parameter <code>{{{signature}}}</code> to value <code>Me</code>. Now, transcluding the template again without passing any parameter, results in the following:
<!-- strictly speaking, this example is false, because the template call was changed to obtain the desired effect - but the effect is the same if the template is defined as described -->
{{Thankyou|reason=everything|signature=Me}}

===Control template inclusion===
By default, the whole content of a template will be processed and displayed both when the template page is being viewed directly and when the template is being included in another page. However, you can control template inclusion by the use of <code><nowiki><noinclude></nowiki></code> and
<code><nowiki><includeonly></nowiki></code> tags.

Anything between <code><nowiki><noinclude></nowiki></code> and <code><nowiki></noinclude></nowiki></code> will be processed and displayed only when the template's page is being viewed directly, and will not be processed and displayed when it is included in another page. The application of this is to do things to the template page that should not be similarly done to the pages where it is included:

* [[Help:Categories|Categorising]] the template.
* Placing in the template [[Help:Links#Interlanguage links|interlanguage links]] to similar templates in other languages.
* Presenting explanatory text about how to use the template.

Anything between <code><nowiki><includeonly></nowiki></code> and <code><nowiki></includeonly></nowiki></code> will be processed and displayed only when the page is being included, and will not be processed and displayed when the template page is being viewed directly. The application of this is to do things in the pages where the template is included that you do not want to be similarly done in the template page:

* [[Help:Categories|Categorising]] only the pages where the template is included. Note that when you change the categories applied by a template in this fashion, the categorization of all the pages where that template is included may not be updated until some time later: this is handled by the {{mediawiki|Manual:Job queue|job queue}}. To force the re-categorisation of a particular page, open the page for edit and save it without changes.
* Ensuring that the template's code is not executed when viewing the template page itself. Normally this is because it isn't receiving any parameters and its execution without parameters has an undesired aspect.

Of course, everything outside <code><nowiki><noinclude></nowiki></code> and
<code><nowiki><includeonly></nowiki></code> tags is processed and displayed both when the template page is being viewed directly and when the template is being included in another page.

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

To find them, users can:
# Click '''Special Pages > All Pages'''
# In the '''Namespace''' list, choose '''Template''' and click '''Go'''.

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

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

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