Joomla! Documentation™

Joomla! 

3.x

Tutorial

Developing an MVC Component

Articles in This Series

1. Introduction
2. Developing a Basic Component
3. Adding a View to the Site Part
4. Adding a Menu Type to the Site Part
5. Adding a Model to the Site Part
6. Adding a Variable Request in the Menu Type
7. Using the Database
8. Basic Backend
9. Adding Language Management
10. Adding Backend Actions
11. Adding Decorations to the Backend
12. Adding Verifications
13. Adding Categories
14. Adding Configuration
15. Adding ACL
16. Adding an Install/Uninstall/Update Script File
17. Adding a Frontend Form
18. Adding an Image
19. Adding a Map
20. Adding AJAX
21. Adding an Alias
22. Using the Language Filter Facility
23. Adding a Modal
24. Adding Associations
25. Adding Checkout
26. Adding Ordering
27. Adding Levels
28. Adding Versioning
29. Adding Tags
30. Adding Access
31. Adding a Batch Process
32. Adding Cache
33. Adding a Feed
34. Adding an Update Server
35. Adding Custom Fields
36. Upgrading to Joomla4

This is a multiple-article series of tutorials on how to develop a Model-View-Controller Component for Joomla! Version.

Begin with the Introduction, and navigate the articles in this series by using the navigation button at the bottom or the box to the right (the Articles in this series).

Note

• This tutorial is part of the Developing a MVC Component for Joomla! 3.x tutorial. You are encouraged to read the previous parts of the tutorial before reading this.

• You can follow the steps below to add a view to the Hello World! component, or you can directly download the archive

• As you follow through the steps of the tutorial you may find problems. In this case you may find it useful to read the Joomla page on How to debug your code.

• You can watch a video associated with this step in the tutorial at Step 2, Adding a View.

Adding a View to Hello World!

In this article we will cover how to add a view to a basic Joomla! component. For this example we will be continuing our work on the Hello World! component.

There are several ways to update a Joomla! component. In this tutorial we will focus option 2.

1	Manually add the files into <path_to_joomla>/
2	Update using the Joomla! Extension Manager and the original directory, non-compressed, used for the component install
3	Update using the Joomla! Extension Manager and an Update Server

To add a view you will need to navigate to com_helloworld, which is the original directory we made for our component. Using your preferred file manager, create or update the following files; as you create or update the files, add the source code for each file which is found in File Details.

1	Update: helloworld.php	<path_to_com_helloworld>/site/helloworld.php
2	Create: controller.php	<path_to_com_helloworld>/site/controller.php
3	Create: index.html	<path_to_com_helloworld>/site/views/index.html
4	Create: index.html	<path_to_com_helloworld>/site/views/helloworld/index.html
5	Create: view.html.php	<path_to_com_helloworld>/site/views/helloworld/view.html.php
6	Create: default.php	<path_to_com_helloworld>/site/views/helloworld/tmpl/default.php
7	Create: index.html	<path_to_com_helloworld>/site/views/helloworld/tmpl/index.html
8	Update: helloworld.xml	<path_to_com_helloworld/helloworld.xml

Updating the Hello World! Component

To update the Hello World! Component in the Joomla! website, please follow the same steps for the original installation.

File Details

site/helloworld.php (Note that some browsers may not copy and paste highlighted text correctly into a text editor. If you find this, then please try a different browser).

<?php
/**
 * @package     Joomla.Administrator
 * @subpackage  com_helloworld
 *
 * @copyright   Copyright (C) 2005 - 2018 Open Source Matters, Inc. All rights reserved.
 * @license     GNU General Public License version 2 or later; see LICENSE.txt
 */

// No direct access to this file
defined('_JEXEC') or die('Restricted access');

// Get an instance of the controller prefixed by HelloWorld
$controller = JControllerLegacy::getInstance('HelloWorld');

// Perform the Request task
$input = JFactory::getApplication()->input;
$controller->execute($input->getCmd('task'));

// Redirect if set by the controller
$controller->redirect();

site/controller.php

<?php
/**
 * @package     Joomla.Administrator
 * @subpackage  com_helloworld
 *
 * @copyright   Copyright (C) 2005 - 2018 Open Source Matters, Inc. All rights reserved.
 * @license     GNU General Public License version 2 or later; see LICENSE.txt
 */
// No direct access to this file
defined('_JEXEC') or die('Restricted access');
/**
 * Hello World Component Controller
 *
 * @since  0.0.1
 */
class HelloWorldController extends JControllerLegacy
{
}

site/views/helloworld/view.html.php

<?php
/**
 * @package     Joomla.Administrator
 * @subpackage  com_helloworld
 *
 * @copyright   Copyright (C) 2005 - 2018 Open Source Matters, Inc. All rights reserved.
 * @license     GNU General Public License version 2 or later; see LICENSE.txt
 */

// No direct access to this file
defined('_JEXEC') or die('Restricted access');

/**
 * HTML View class for the HelloWorld Component
 *
 * @since  0.0.1
 */
class HelloWorldViewHelloWorld extends JViewLegacy
{
	/**
	 * Display the Hello World view
	 *
	 * @param   string  $tpl  The name of the template file to parse; automatically searches through the template paths.
	 *
	 * @return  void
	 */
	function display($tpl = null)
	{
		// Assign data to the view
		$this->msg = 'Hello World';

		// Display the view
		parent::display($tpl);
	}
}

site/views/helloworld/tmpl/default.php

<?php
/**
 * @package     Joomla.Administrator
 * @subpackage  com_helloworld
 *
 * @copyright   Copyright (C) 2005 - 2018 Open Source Matters, Inc. All rights reserved.
 * @license     GNU General Public License version 2 or later; see LICENSE.txt
 */
 
// No direct access to this file
defined('_JEXEC') or die('Restricted access');
?>
<h1><?php echo $this->msg; ?></h1>

index.html Note - the same code is used for all folders

<html><body bgcolor="#FFFFFF"></body></html>

helloworld.xml

<?xml version="1.0" encoding="utf-8"?>
<extension type="component" version="3.0" method="upgrade">

	<name>Hello World!</name>
	<!-- The following elements are optional and free of formatting constraints -->
	<creationDate>January 2018</creationDate>
	<author>John Doe</author>
	<authorEmail>john.doe@example.org</authorEmail>
	<authorUrl>http://www.example.org</authorUrl>
	<copyright>Copyright Info</copyright>
	<license>License Info</license>
	<!--  The version string is recorded in the components table -->
	<version>0.0.2</version>
	<!-- The description is optional and defaults to the name -->
	<description>Description of the Hello World component ...</description>

	<update> <!-- Runs on update; New since J2.5 -->
		<schemas>
			<schemapath type="mysql">sql/updates/mysql</schemapath>
		</schemas>
	</update>

	<!-- Site Main File Copy Section -->
	<!-- Note the folder attribute: This attribute describes the folder
		to copy FROM in the package to install therefore files copied
		in this section are copied from /site/ in the package -->
	<files folder="site">
		<filename>index.html</filename>
		<filename>helloworld.php</filename>
		<filename>controller.php</filename>
		<folder>views</folder>
	</files>

	<administration>
		<!-- Administration Menu Section -->
		<menu link='index.php?option=com_helloworld'>Hello World!</menu>
		<!-- Administration Main File Copy Section -->
		<!-- Note the folder attribute: This attribute describes the folder
			to copy FROM in the package to install therefore files copied
			in this section are copied from /admin/ in the package -->
		<files folder="admin">
			<!-- Admin Main File Copy Section -->
			<filename>index.html</filename>
			<filename>helloworld.php</filename>
			<!-- SQL files section -->
			<folder>sql</folder>
		</files>
	</administration>

</extension>

Code Explanation

In case you were curious as to why this works the way it does.

helloworld.php

defined('_JEXEC') or die('Restricted access');

This enables for a secure entry point into the Joomla! platform. JEXEC contains a detailed explanation.

$controller = JControllerLegacy::getInstance('HelloWorld');

JControllerLegacy is a base class for a Joomla! Controller. In order for our website to use controllers, we must extend this class in our component. The getInstance static method of the JControllerLegacy class will create a controller. In the code above, it will instantiate a controller object of a class named HelloWorldController. Joomla will look for the declaration of that class in <path_to_joomla>/htdocs/components/com_helloworld/controller.php.

$input = JFactory::getApplication()->input;
$controller->execute($input->getCmd('task'));

After the controller is created, we instruct the controller to execute the task, as defined in the URL: <yoursite>/joomla/index.php?option=com_helloworld&task=<task_name>. If no task is set, the default task 'display' will be assumed. When display is used, the 'view' variable will decide what will be displayed. Other common tasks are save, edit, new, etc.

$controller->redirect();

The controller might decide to redirect the page, usually after a task like 'save' has been completed. This last statement takes care of the actual redirection.

The main entry point, helloworld.php, essentially passes control to the controller, which handles performing the task that was specified in the request. Our component specific controller doesn't do anything more than the parent class already does, which is why our controller class is empty.

controller.php

class HelloWorldController extends JControllerLegacy
{
}

When no task is given in the request variables, the default task will be executed. It's the display task by default. The JControllerLegacy class has such a task. In our example, it will display a view named HelloWorld.

view.html.php

class HelloWorldViewHelloWorld extends JViewLegacy
{
	function display($tpl = null)
	{
		// Assign data to the view
		$this->msg = 'Hello World';
 
		// Display the view
		parent::display($tpl);
	}
}

The view sets up the text to be output and then calls the base display class. JViewLegacy is a base class for a Joomla! View. In our case, this method will display data using the tmpl/default.php file.

Caveat: If your view needs to load or otherwise embed individual JavaScript code, do not do that in the view, as the code might not get included when caching is enabled. Load those scripts in the controller instead. See the related issue on the issue tracker.

default.php

<h1><?php echo $this->msg; ?></h1>

This template file will be included by the JViewLegacy class. Therefore, here, $this refers to the HelloWorldViewHelloWorld class.

helloworld.xml

<version>0.0.2</version>

Updates the version number.

<filename>controller.php</filename>
<folder>views</folder>

Tells installer application to add controller.php and the views/directory

Component Contents

At this point in the tutorial, your component should contain the following files:

1	helloworld.xml	this is an XML (manifest) file that tells Joomla! how to install our component.
2	site/helloworld.php	this is the site entry point to the Hello World! component
3	site/index.html	prevents web server from listing directory content
4	site/controller.php	file representing the controller
5	site/views/index.html	prevents web server from listing directory content
6	site/views/helloworld/index.html	prevents web server from listing directory content
7	site/views/helloworld/view.html.php	file representing the view
8	site/views/helloworld/tmpl/index.html	prevents web server from listing directory content
9	site/views/helloworld/tmpl/default.php	the default view
10	admin/index.html	prevents web server from listing directory content
11	admin/helloworld.php	this is the administrator entry point to the Hello World! component
12	admin/sql/index.html	prevents web server from listing directory content
13	admin/sql/updates/index.html	prevents web server from listing directory content
14	admin/sql/updates/mysql/index.html	prevents web server from listing directory content
15	admin/sql/updates/mysql/0.0.1.sql	file allowing to initialise schema version of the com_helloworld component.

General Information

Prev: Developing a Basic Component

Next: Adding a menu type to the site part