Extension:Cargo/Quick start guide

Let's say that you want to create a wiki that shows all the books you have at home. You want two kinds of pages on your wiki: one for books, and one for authors. Each book page should hold a title, an author name (or names), a genre (or genres), a year of publication, and a number of pages. Each author page should hold the author name, their country of origin, and a list of all the books they have written that you own.

The only thing you need to do is create two templates, one for books and one for authors. Here is what the two templates might look like:

Template:Book This is the "Book" template.

Template:Author This is the "Author" template.

That is all you need to do to have infobox-style templates that both define a data structure and store their data in an easily-queried way.

You can see in this template examples of calls to the three main parser functions of Cargo: #cargo_declare, #cargo_store and #cargo_query; and hopefully how the three interact together. Note especially the placement of #cargo_declare and #cargo_store: the former in the &lt;noinclude&gt; tag, the latter in the &lt;includeonly&gt; tag.

A few other notes on these templates:
 * For both templates, the name of the entity, i.e the name of the book or author, is not stored in the template. That is because the name of the page itself will hold the name of that book or author -- and will also be stored in those two tables, in a field named "_pageName".
 * The "Author" template contains, at the end, what is known as an aggregating query, that queries the "Books" table (defined by the other template) and gets the names of all the pages that have the current page among its values for the "Authors" field. (It will then, by default, display that information in a comma-separated list.) This is a very common type of query; it means that you don't need to store the same data in two different pages, because one page can simply query the data.
 * There is one line of this sample code that requires another extension to work: the line in Template:Book which includes calls to both #arraymap and #formredlink, both of which are defined by the Semantic Forms extension. This line does a rather complex operation: it separates the value of " " into one or more sub-values (splitting by comma), then, for each value, either links directly to that page, if a page with that name already exists; or links to the form for creating that page, using the form definition at "Form:Author". Thus, this template presupposes not only that the Semantic Forms extension is installed, but that an "Author" form has been created. If you don't have Semantic Forms installed, you could replace that line with something a lot simpler, like:
 * However, Semantic Forms is strongly recommended for any wiki that uses Cargo.