Obsolete:Output API

Moodle 2.0

Note: This article is a work in progress. Please use the page comments or an appropriate moodle.org forum for any recommendations/suggestions for improvement.

This page describes the Output API for Moodle 2.0. It works closely with the Page API, so you may want to refer to that documentation as well.

Components

Components in the Output API are classes that represent elements to be output. They do not contain any code for outputting anything, but they contain rich meta-data that is used by the Renderers to generate output. Some of the key aspects of components are outlined here:

• Components do not have defined constructors. Passing arguments to the default constructor will not do anything useful.
• Components consist mainly of variables with sensible defaults, and a prepare() method which makes use of these variables to setup other defaults prior to rendering.
• The prepare() method always behaves the same way, regardless of which renderer is used. This ensures consistency of the component's variables.
• Additional "shortcut" methods are sometimes added to provide a more high-level API to developers.

moodle_html_component

This is the base class for all output components. It is not declared as abstract, because you could actually use it to instantiate a basic component. However, almost all rendering functions will expect a sub-class of this class as a parameter, so instantiating it is unlikely to be very useful.

This class basically holds data and useful functions that can apply to any component, such as id, classes, style, alt and title (HTML attributes valid for any XHTML element). It also handles the collection and setting up of component_actions, which are described below. Refer to the class' PHP docs for details on variables and functions.

This class also defines a function for generating unique HTML ids for components that require one, and holds a static array for generated ids to prevent duplication.

HTML low-level components

This list of components replicate basic HTML elements. They are prefixed with html_ to make it clear that they are the basic building blocks of the output API.

html_label

Many HTML elements may have a label (input fields, dropdowns etc.). Some rendering functions look for this label and render it accordingly.

html_label requires a $text value, and should be given a $for value for accessibility reasons. It is rendered ultimately by $OUTPUT->label(html_label $label).

html_field

• Represents a HTML input field. Can be used to output any input type, although some of its variables only apply to some types (e.g. maxlength only applies to text inputs).
• It has a shortcut method for preparing a text input: make_text($name, $value, $alt, $maxlength).
• It has an optional $label variable which can either be set as a string, or as a html_label component. If a string is given, the prepare() method will turn it into a html_label, generate an ID for the input if not already done, and use that ID as the $for value of the html_label.

Moodle components

The following components do not map exactly to HTML elements, so they are prefixed with moodle_.