View source for Help:Multiple-instance templates

'''Multiple-instance templates''' refer to the use of a series of instances of the same [[Help:Templates|(wiki) template]] on a single wiki page, usually with unique data assigned to each instance. For instance, instances of a template may be used to list the contacts of a company, the ingredients of a recipe, the stories in a book, etc. In this way, you can present items of the same type in a uniform manner and streamline structured data so that they can be stored in the database.

The term is typically used in the context of managing such a list of template instances by way of a form (see the form extensions below) as well as itemising data to be stored in the database (see the data storage extensions below).

Structurally, multiple-instance templates can be either top-level templates or children of a parent template. A child template is an instance of a template assigned to a parameter of the parent template. A top-level template is not nested in this way and may or may not behave as a parent template for one or multiple child templates. Deeper levels of nesting templates are not impossible, but lack support in form extensions.

== Example ==
The ingredients of some recipe for salad : 

<pre>
{{Recipe
|Title=My favourite salad
|Ingredients={{Ingredient
 |Item=Romaine lettuce
 |Quantity=Four leaves.
 |Preparation=Torn.
}}{{Ingredient
 |Item=Radish
 |Quantity=Six radishes.
 |Preparation=Chopped.
}}{{Ingredient
 |Item=Tomato
 |Quantity=2 tomatoes.
 |Preparation=Chopped.
}}{{Ingredient
 |Item=Licame
 |Quantity=A small one.
 |Preparation=Peeled and julienned.
}}
}}</pre>

(etc.)

== Form extensions ==
A number of [[Help:Extensions|extensions]] are available that let you use a form to manage template instances more easily. 

* [[Extension:Page Forms]]: see especially [[Extension:Page Forms/Defining forms#Multiple-instance templates |this help page]]. The term 'multiple-instance templates' was likely coined for this extension.  
* [[Extension:FlexForm]]: offers similar support. See especially [https://www.open-csp.org/DevOps:Doc/FlexForm/2.1/instance this help page].

== Data storage extensions ==
Template instances can be used as containers for structured data. The following extensions offer parser functions that can be used in a template to store data:

* [[Extension:Semantic MediaWiki]] (SMW) - offers the [https://www.semantic-mediawiki.org/wiki/Subobject <code>#subobject</code> parser function] for self-contained units of property-value pairs as well as [https://www.semantic-mediawiki.org/wiki/Help:Type_Record a data type called Record].
* [[Extension:Cargo]] - offers <code>#cargo_declare</code> and <code>#cargo_store</code>, which can be used in a way similar to SMW's subobjects. 

== See also ==
* [[Help:Tabular data]]
* [[Manual:Managing data in MediaWiki]]

[[Category:Template]]