Introduction
The new framework in Joomla! 1.5 unleashes a great deal of power for developers. The code has been completely overhauled and cleaned up. This tutorial will guide you through the process of developing a component using this new framework.
The scope of this project will be to develop a simple Hello World! component. In future tutorials, this simple framework will be built upon to show the full power and versatility of the MVC design pattern in Joomla!
Requirements
You need Joomla! 1.5 or greater for this tutorial.
Introduction to Model-View-Controller
While the idea behind a component may seem extremely simple, code can quickly become very complex as additional features are added or the interface is customized.
Model-View-Controller (herein referred to as MVC) is a software design pattern that can be used to organize code in such a way that the business logic and data presentation are separate. The premise behind this approach is that if the business logic is grouped into one section, then the interface and user interaction that surrounds the data can revised and customized without having to reprogram the business logic.
There are three main parts of an MVC component. They are described here in brief, but for a more thorough explanation, please refer to the links provided at the end of this tutorial.
Model
The model is the part of the component that encapsulates the application’s data. It will often provide routines to manage and manipulate this data in a meaningful way in addition to routines that retrieve the data from the model. In our case, the model will contain methods to add, remove and update information about the greetings in the database. It will also contain methods to retrieve the list of greetings from the database. In general, the underlying data access technique should be encapsulated in the model. In this way, if an application is to be moved from a system that utilizes a flat file to store its information to a system that uses a database, the model is the only element that needs to be changed, not the view or the controller.
View
The view is the part of the component that is used to render the data from the model in a manner that is suitable for interaction. For a web-based application, the view would generally be an HTML page that is returned to the data. The view pulls data from the model (which is passed to it from the controller) and feeds the data into a template which is populated and presented to the user. The view does not cause the data to be modified in any way, it only displays data retrieved from the model.
Controller
The controller is responsible for responding to user actions. In the case of a web application, a user action is (generally) a page request. The controller will determine what request is being made by the user and respond appropriately by triggering the model to manipulate the data appropriately and passing the model into the view. The controller does not display the data in the model, it only triggers methods in the model which modify the data, and then pass the model into the view which displays the data.
Joomla! MVC Implementation
In Joomla!, the MVC pattern is implemented using three classes: <classname>JModel</classname>, <classname>JView</classname> and <classname>JController</classname>. For more detailed information about these classes, please refer to the API reference documentation (WIP).
Creating a Component
For our basic component, we only require five files:
* hello.php - this is the entry point to our component
* controller.php - this file contains our base controller
* views/hello/view.html.php - this file retrieves the necessary data and pushes it into the template
* views/hello/tmpl/default.php - this is the template for our output
* hello.xml - this is an XML file that tells Joomla! how to install our component.
Creating the Entry Point
Joomla! is always accessed through a single point of entry: index.php for the Site Application or administrator/index.php for the Administrator Application. The application will then load the required component, based on the value of ‘option’ in the URL or in the POST data. For our component, the URL would be:
index.php?option=com_hello&view=hello This will load our main file, which can be seen as the single point of entry for our component: components/com_hello/hello.php.
The code for this file is fairly typical across components.
- Código: Seleccionar todo
<?php
/**
* @package Joomla.Tutorials
* @subpackage Components
* components/com_hello/hello.php
* @link http://dev.joomla.org/component/option,com_jd-wiki/Itemid,31/id,tutorials:modules/
* @license GNU/GPL
*/
// no direct access
defined( '_JEXEC' ) or die( 'Restricted access' );
// Require the base controller
require_once( JPATH_COMPONENT.DS.'controller.php' );
// Require specific controller if requested
if($controller = JRequest::getWord('controller')) {
$path = JPATH_COMPONENT.DS.'controllers'.DS.$controller.'.php';
if (file_exists($path)) {
require_once $path;
} else {
$controller = '';
}
}
// Create the controller
$classname = 'HelloController'.$controller;
$controller = new $classname( );
// Perform the Request task
$controller->execute( JRequest::getVar( 'task' ) );
// Redirect if set by the controller
$controller->redirect();
?>
