Difference between revisions of "Developing a MVC Component/Using the database"

Revision as of 09:06, 19 November 2010

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Articles in this series[edit]

Introduction[edit]

This tutorial is part of the Developing a Model-View-Controller (MVC) Component for Joomla!1.6 tutorial. You are encouraged to read the previous parts of the tutorial before reading this.

Using the database[edit]

Components usually manage their contents using the database. During the install/uninstall/update phase of a component, you can execute SQL queries through the use of SQL text files.

With your favorite file manager and editor put a file admin/sql/install.mysql.utf8.sql containing:

admin/sql/install.mysql.utf8.sql

DROP TABLE IF EXISTS `#__helloworld`;

CREATE TABLE `#__helloworld` (
	`id` INT(11) NOT NULL auto_increment,
	`greeting` VARCHAR(25) NOT NULL,
	PRIMARY KEY  (`id`)
) ENGINE=MyISAM AUTO_INCREMENT=0 DEFAULT CHARSET=utf8;

INSERT INTO `#__helloworld` (`greeting`) VALUES
	('Hello World!'),
	('Good bye World!');

This is the install file. It will be executed if your put an appropriate order in the helloworld.xml file

helloworld.xml

<?xml version="1.0" encoding="utf-8"?>
<extension type="component" version="1.6.0" method="upgrade">
	<name>Hello World!</name>
	<creationDate>November 2009</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>
	<version>0.0.6</version>
	<description>Description of the Hello World component ...</description>

	<install> <!-- Runs on install -->
		<sql>
			<file driver="mysql" charset="utf8">sql/install.mysql.utf8.sql</file>
		</sql>
	</install>
	<uninstall> <!-- Runs on uninstall -->
		<sql>
			<file driver="mysql" charset="utf8">sql/uninstall.mysql.utf8.sql</file>
		</sql>
	</uninstall>
	<update> <!-- Runs on update -->
		<sql>
			<file driver="mysql" charset="utf8">sql/update.mysql.utf8.sql</file>
		</sql>
	</update>

	<files folder="site">
		<filename>index.html</filename>
		<filename>helloworld.php</filename>
		<filename>controller.php</filename>
		<folder>views</folder>
		<folder>models</folder>
	</files>

	<administration>
		<menu>Hello World!</menu>
		<files folder="admin">
			<filename>index.html</filename>
			<filename>helloworld.php</filename>
			<!-- SQL files section -->
			<folder>sql</folder>
			<!-- tables files section -->
			<folder>tables</folder>
			<!-- models files section -->
			<folder>models</folder>
		</files>		
	</administration>
</extension>

Do the same for the uninstall and update files:

With your favorite file manager and editor put a file admin/sql/uninstall.mysql.utf8.sql containing:

admin/sql/uninstall.mysql.utf8.sql

DROP TABLE IF EXISTS `#__helloworld`;

With your favorite file manager and editor put a file admin/sql/update.mysql.utf8.sql containing:

admin/sql/update.mysql.utf8.sql

DROP TABLE IF EXISTS `#__helloworld`;

CREATE TABLE `#__helloworld` (
	`id` INT(11) NOT NULL auto_increment,
	`greeting` VARCHAR(25) NOT NULL,
	PRIMARY KEY  (`id`)
) ENGINE=MyISAM AUTO_INCREMENT=0 DEFAULT CHARSET=utf8;

INSERT INTO `#__helloworld` (`greeting`) VALUES
	('Hello World!'),
	('Good bye World!');

Adding a new field type[edit]

For the moment, we have used a hard coded field type for messages. We need to use our database for choosing the message.

Modify the site/views/helloworld/tmpl/default.xml file and put these lines

site/views/helloworld/tmpl/default.xml

<?xml version="1.0" encoding="utf-8"?>

<metadata>

	<layout title="com_helloworld_HelloWorld_View_Default_Title">

		<message>com_helloworld_HelloWorld_View_Default_Desc</message>

	</layout>
	<fields
		name="request"
		addfieldpath="/administrator/components/com_helloworld/models/fields"
	>
		<fieldset name="request">
			<field
				id="id"
				name="id"
				type="helloworld"
				label="com_helloworld_HelloWorld_View_Default_Msg_Label"
				description="com_helloworld_HelloWorld_View_Default_Msg_Desc"
			/>
		</fieldset>
	</fields>

</metadata>

It introduces a new field type and tells Joomla to look for the field definition in the /administrator/components/com_helloworld/models/fields folder.

With your favorite file manager and editor put a file admin/models/fields/helloworld.php file containing:

admin/models/fields/helloworld.php

<?php
// No direct access to this file
defined('_JEXEC') or die;
// import the list field type
jimport('joomla.html.html.list');
/**
 * HelloWorld Form Field class for the HelloWorld component
 */
class JFormFieldHelloWorld extends JFormFieldList
{
	/**
	 * The field type.
	 *
	 * @var		string
	 */
	protected $type = 'HelloWorld';
	/**
	 * Method to get a list of options for a list input.
	 *
	 * @return	array		An array of JHtml options.
	 */
	protected function getOptions() 
	{
		$db = JFactory::getDBO();
		$query = new JDatabaseQuery;
		$query->select('id,greeting');
		$query->from('#__helloworld');
		$db->setQuery($query);
		$messages = $db->loadObjectList();
		$options = array();
		foreach($messages as $message) 
		{
			$options[] = JHtml::_('select.option', $message->id, $message->greeting);
		}
		$options = array_merge(parent::getOptions() , $options);
		return $options;
	}
}

The new field type displays a drop-down list of messages to choose from. You can see the result of this change in the menu manager section for the helloworld item.

Display the chosen message[edit]

When a menu item of this component is created/updated, Joomla stores the identifier of the message. The HelloWorldModelHelloWorld model has now to compute the message according to this identifier and the data stored in the database.

Modify the site/models/helloworld.php file:

site/models/helloworld.php

<?php
// No direct access to this file
defined('_JEXEC') or die('Restricted access');
// import Joomla modelitem library
jimport('joomla.application.component.modelitem');
/**
 * HelloWorld Model
 */
class HelloWorldModelHelloWorld extends JModelItem
{
	/**
	 * @var string msg
	 */
	protected $msg;
	/**
	 * Get the message
	 * @return string The message to be displayed to the user
	 */
	public function getMsg() 
	{
		if (!isset($this->msg)) 
		{
			$id = JRequest::getInt('id');
			// Get a TableHelloWorld instance
			$table = $this->getTable();
			// Load the message
			$table->load($id);
			// Assign the message
			$this->msg = $table->greeting;
		}
		return $this->msg;
	}
}

The model now asks the TableHelloWorld to get the message. This table class has to be defined in admin/tables/helloworld.php file

admin/tables/helloworld.php

<?php
// No direct access
defined('_JEXEC') or die('Restricted access');
// import Joomla table library
jimport('joomla.database.table');
/**
 * Hello Table class
 */
class TableHelloWorld extends JTable
{
	/**
	 * Primary Key
	 *
	 * @var int
	 */
	var $id = null;
	/**
	 * @var string
	 */
	var $greeting = null;
	/**
	 * Constructor
	 *
	 * @param object Database connector object
	 */
	function TableHelloWorld(&$db) 
	{
		parent::__construct('#__helloworld', 'id', $db);
	}
}

You shouldn't see any differences, but if you access the database you should see a table named jos_helloworld with two columns: id and greeting. And two entries: Hello World! and Good bye World

Packaging the component[edit]

Content of your code directory

Create a compressed file of this directory or directly download the archive and install it using the extension manager of Joomla!1.6. You can add a menu item of this component using the menu manager in the backend.

Navigate[edit]

Prev: Adding a variable request in the menu type Prev: Basic backend

Contributors[edit]

Christophe Demko

Italic text

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