Creating a Hello World for Joomla 15

Creating a Hello World Module for Joomla! 1.5

A module is a lightweight and flexible extension that is used for page rendering. They are used for

small bits of the page that are generally less complex and are able to be seen across different

components.

You can see many examples of modules in the standard Joomla! install: - menus - Latest News -

Login form - and many more.

This tutorial will explain how to go about creating a simple Hello World module. Through this

tutorial you will learn the basic file structure of a module. This basic structure can then be

expanded to produce more elaborate modules.

File Structure

There are four basic files that are used in the standard pattern of module development: *

mod_helloworld.php - This file is the main entry point for the module. It will perform any necessary

initialization routines, call helper routines to collect any necessary data, and include the template

which will display the module output.

mod_helloworld.xml - This file contains information about the module. It defines the files

that need to be installed by the Joomla! installer and specifies configuration parameters for

the module.

helper.php - This file contains the helper class which is used to do the actual work in

retrieving the information to be displayed in the module (usually from the database or some

other source).

tmpl/default.php - This is the module template. This file will take the data collected by

mod_helloworld.php and generate the HTML to be displayed on the page.

Creating mod_helloworld.php

The mod_helloworld.php file will perform three tasks:

include the helper.php file which contains the class to be used to collect the necessary data

invoke the appropriate helper class method to retrieve the data

include the template to display the output.

The helper class is defined in our helper.php file. This file is included with a require_once statement:

require_once( dirname(__FILE__).DS.'helper.php' );

require_once is used because our helper functions are defined within a class, and we only want the

class defined once.

Our helper class has not been defined yet, but when it is, it will contain one method: getHello(). For

our basic example, it is not really necessary to do this - the “Hello, World” message that this

method returns could simply be included in the template. We use a helper class here to

demonstrate this basic technique.

Our module currently does not use any parameters, but we will pass them to the helper method

anyway so that it can be used later if we decide to expand the functionality of our module.

The helper class method is invoked in the following way:

$hello = modHelloWorldHelper::getHello( $params );

Completed mod_helloworld.php file

The complete mod_helloworld.php file is as follows:

<?php

/**

* Hello World! Module Entry Point

*

* @package Joomla.Tutorials

* @subpackage Modules

* @link

http://dev.joomla.org/component/option,com_jd-wiki/Itemid,31/id,tutorials:modules/

* @license GNU/GPL, see LICENSE.php

* mod_helloworld is free software. This version may have been modified pursuant

* to the GNU General Public License, and as distributed it includes or

* is derivative of works licensed under the GNU General Public License or

* other free or open source software licenses.

*/

// no direct access

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

// Include the syndicate functions only once

require_once( dirname(__FILE__).DS.'helper.php' );

$hello = modHelloWorldHelper::getHello( $params );

require( JModuleHelper::getLayoutPath( 'mod_helloworld' ) );

The one line that we haven’t explained so far is the first line. This line checks to make sure that this

file is being included from the Joomla! application. This is necessary to prevent variable injection

and other potential security concerns.

Creating helper.php

The helper.php file contains that helper class that is used to retrieve the data to be displayed in the

module output. As stated earlier, our helper class will have one method: getHello(). This method will

return the ‘Hello, World’ message.

Here is the code for the helper.php file:

<?php

/**

* Helper class for Hello World! module

*


* @subpackage Modules

* @link


* @license GNU/GPL, see LICENSE.php

* mod_helloworld is free software. This version may have been modified pursuant

* to the GNU General Public License, and as distributed it includes or

* is derivative of works licensed under the GNU General Public License or

* other free or open source software licenses.

*/

class modHelloWorldHelper

{

/**

* Retrieves the hello message

*

* @param array $params An object containing the module parameters

* @access public

*/

function getHello( $params )

{

return 'Hello, World!';

}

}

There is no rule stating that we must name our helper class as we have, but it is helpful to do this

so that it is easily identifiable and locateable.

More advanced modules might include database requests or other functionality in the helper class

method.

Creating tmpl/default.php

The default.php file is the template which displays the module output.

The code for the default.php file is as follows:

<?php // no direct access

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

<?php echo $hello; ?>

An important point to note is that the template file has the same scope as the mod_helloworld.php

file. What this means is that the variable $hello can be defined in the mod_helloworld.php file and

then used in the $hello file without any extra declarations or function calls.

Creating mod_helloworld.xml

The mod_helloworld.xml is used to specify which files the installer needs to copy and is used by the

Module Manager to determine which parameters are used to configure the module. Other

information about the module is also specified in this file.

The code for mod_helloworld.xml is as follows:

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

<install type="module" version="1.5.0">

<name>Hello, World!</name>

<author>John Doe</author>

<version>1.5.0</version>

<description>A simple Hello, World! module.</description>

<files>

<filename module="mod_helloworld">mod_helloworld.php</filename>

<filename>index.html</filename>

<filename>helper.php</filename>

<filename>tmpl/default.php</filename>

<filename>tmpl/index.html</filename>

</files>

<params>

</params>

</install>

You will notice that there are two additional files that we have not yet mentioned: index.html and

tmpl/index.html. These files are included so that these directories cannot be browsed. If a used

attempts to point their browser to these folders, the index.html file will be displayed. These files

can be left empty or can contain the simple line:

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

which will display an empty page.

Since our module does not use any parameters, this section is empty.

Conclusion

Module development for Joomla! is a fairly simple, straightforward process. Using the techniques

described in this tutorial, an endless variety of modules can be developed with little hassle.

Developing a Model-View-Controller Component - Part 1

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.

<?php

/**


* @subpackage Components

* components/com_hello/hello.php

* @link


* @license GNU/GPL

*/

// no direct 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();

?>

The first statement is a security check.

JPATH_COMPONENT is the absolute path to the current component, in our case

components/com_hello. If you specifically need either the Site component or the Administrator

component, you can use JPATH_COMPONENT_SITE or JPATH_COMPONENT_ADMINISTRATOR.

DS is the directory separator of your system: either ‘/’ or ‘\’. This is automatically set by the

framework so the developer doesn’t have to worry about developing different versions for different

server OSs. DS should always be used when referring to files on the local server.

After loading the base controller, we check if a specific controller is needed. In this component, the

base controller is the only controller, but we will leave this here for future use.

<classname>JRequest</classname>:getVar() finds a variable in the URL or the POST data. So if our

URL is index.php?option=com_hello>controller=controller_name, then we can retrieve our

controller name in our component using: echo

<classname>JRequest</classname>::getVar(’controller’);

Now we have our base controller ‘<classname>HelloController</classname>’ in

com_hello/controller.php, and, if needed, additional controllers like

‘<classname>HelloControllerController1</classname>’ in com_hello/controllers/controller1.php.

Using this standard naming scheme will make things easy later on: ‘{Componentname}

{Controller}{Controllername}’

After the controller is created, we instruct the controller to execute the task, as defined in the URL:

index.php?option=com_hello&task=sometask. 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...

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 (hello.php) essentially passes control to the controller, which handles

performing the task that was specified in the request.

Creating the Controller

Our component only has one task - greet the world. Therefore, the controller will be very simple. No

data manipulation is required. All that needs to be done is the appropriate view loaded. We will

have only one method in our controller: display(). Most of the required functionality is built into the

JController class, so all that we need to do is invoke the JController::display() method.

The code for the base controller is:

<?php

/**



* @link


* @license GNU/GPL

*/

// no direct access


jimport('joomla.application.component.controller');

/**

* Hello World Component Controller

*



*/

class HelloController extends JController

{

/**

* Method to display the view

*

* @access public

*/

function display()

{

parent::display();

}

}

?>

The <classname>JController</classname> constructor will always register a display() task and

unless otherwise specified (using the registerDefaultTask() method), it will set it as the default task.

This barebones display() method isn’t really even necessary since all it does is invoke the parent

constructor. However, it is a good visual clue to indicate what is happening in the controller.

The <classname>JController</classname>::display() method will determine the name of the view

and layout from the request and load that view and set the layout. When you create a menu item

for your component, the menu manager will allow the administrator to select the view that they

would like the menu link to display and to specify the layout. A view usually refers to a view of a

certain set of data (i.e. a list of cars, a list of events, a single car, a single event). A layout is a way

that that view is organized.

In our component, we will have a single view called hello, and a single layout (default).

Creating the View

The task of the view is very simple: It retrieves the data to be displayed and pushes it into the

template. Data is pushed into the template using the <classname>JView</classname>::assignRef

method.

The code for the view is:

<?php

/**



* @link


* @license GNU/GPL

*/

// no direct access


jimport( 'joomla.application.component.view');

/**

* HTML View class for the HelloWorld Component

*

* @package HelloWorld

*/

class HelloViewHello extends JView

{

function display($tpl = null)

{

$greeting = "Hello World!";

$this->assignRef( 'greeting', $greeting );

parent::display($tpl);

}

}

?>

Creating the Template

Joomla! templates/layouts are regular PHP files that are used to layout the data from the view in a

particular manner. The variables assigned by the JView::assignRef method can be accessed from

the template using $this→{propertyname} (see the template code below for an example).

Our template is very simple: we only want to display the greeting that was passed in from the view:

<?php // no direct access

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

<h1><?php echo $this->greeting; ?></h1>

Wrapping It All Up - Creating the hello.xml File

It is possible to install a component manually by copying the files using an FTP client and modifying

the database tables. It is more efficient to create a package file that will allow the Joomla! Installer

to do this for you. This package file contains a variety of information:

basic descriptive details about your component (i.e. name), and optionally, a description,

copyright and license information.

a list of files that need to be copied.

optionally, a PHP file that performs additional install and uninstall operations.

optionally, an SQL file which contains database queries that should be executed upon

install/uninstall

The format of the XML file is as follows:


<!DOCTYPE install SYSTEM "http://dev.joomla.org/xml/1.5/component-install.dtd">

<install type="component" version="1.5.0">

<name>Hello</name>



<creationDate>2007 02 22</creationDate>


<authorEmail>[email protected]</authorEmail>

<authorUrl>http://www.example.org</authorUrl>

<copyright>Copyright Info</copyright>

<license>License Info</license>



<version>Component Version String</version>



<description>Description of the component ...</description>





<files folder="site">


<filename>hello.php</filename>

<filename>controller.php</filename>

<filename>views/index.html</filename>

<filename>views/hello/index.html</filename>

<filename>views/hello/view.html.php</filename>

<filename>views/hello/tmpl/index.html</filename>

<filename>views/hello/tmpl/default.php</filename>

</files>

<administration>



<menu>Hello World!</menu>



<files folder="admin">


<filename>admin.hello.php</filename>

</files>

</administration>

</install>

If you look closely you will notice that there are some files that will be copied that we have not

discussed. These are the index.html files. An index.html file is placed in each directory to prevent

prying users from getting a directory listing. If there is no index.html file, some web servers will list

the directory contents. This is often undesirable. These files have the simple line:

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

It will simply display a blank page.

The other file is the admin.hello.php file. This is the entry point for the admin section of our

component. Since we don’t have an admin section of our component, it will have the same content

as the index.html files at this point in time.

Contributors

mjaz

staalanden

Download

The component can be downloaded at: com_hello1.zip

Developing a Model-View-Controller Component - Part 2 - Adding a Model

Introduction

In the first tutorial of this series, creating a simple view-controller component using the Joomla! 1.5

CMS framework was demonstrated.

In the first tutorial, the greeting was hardcoded into the view. This doesn’t follow the MVC pattern

exactly because the view is intended to only display the data, and not contain it.

In this second part of the tutorial we will demonstrate how to move this out of the view and into a

model. In future tutorials we will demonstrate the power and flexibility that this design pattern

provides.

Creating the Model

The concept of model gets its name because this class is intended to represent (or ‘model’) some

entity. In our case, our first model will represent a ‘hello’, or a greeting. This is in line with our

design thus far, because we have one view (’hello’), which is a view of our greeting.

http://dev.joomla.org/components/com_jd-wiki/data/media/components/com_hello1.zip

The naming convention for models in the Joomla! framework is that the class name starts with the

name of the component (in our case ‘hello’, followed by ‘model’, followed by the model name.

Therefore, our model class is called HelloModelHello.

At this point, we will only model one behaviour of our hello, and that is retrieving the greeting. We

will thus have one method, called getGreeting(). It will simply return the string ‘Hello, World!’.

Here is the code for our model class:

<?php

/**

* Hello Model for Hello World Component

*



* @link


* @license GNU/GPL

*/

// Check to ensure this file is included in Joomla!

defined('_JEXEC') or die();

jimport( 'joomla.application.component.model' );

/**

* Hello Model

*



*/

class HelloModelHello extends JModel

{

/**

* Gets the greeting

* @return string The greeting to be displayed to the user

*/

function getGreeting()

{

return 'Hello, World!';

}

}

You will notice a line that starts with jimport. The jimport function is used to load files from the

Joomla! framework that are required for our component. This particular statement will load the

file /libraries/joomla/application/component/model.php. The ‘.’s are used as directory separators

and the last part is the name of the file to load. All files are loaded relative to the libraries directory.

This particular file contains the class definition for the JModel class, which is necessary because our

model extends this class.

Now that we have created our model, we must modify our view so that it uses it to obtain the

greeting.

Using the Model

The Joomla! framework is setup in such a way that the controller will automatically load the model

that has the same name as the view and will push it into the view. Since our view is called ‘Hello’,

our ‘Hello’ model will automatically be loaded and pushed into the view. Therefore, we can easily

retrieve a reference to our model using the JView::getModel() method.

Our previous view code contained the lines:

$greeting = "Hello World!";

To take advantage of our model, we change this line to:

$model =& $this->getModel();

$greeting = $model->getGreeting();

The complete view now looks like:

<?php

/**

* Hello View for Hello World Component

*



* @link


* @license GNU/GPL

*/

// no direct access


jimport( 'joomla.application.component.view');

/**

* HTML View class for the HelloWorld Component

*



*/

class HelloViewHello extends JView

{


{

$model =& $this->getModel();

$greeting = $model->getGreeting();

$this->assignRef( 'greeting', $greeting );


}

}

?>

Adding the File to the Package

All that remains is to add an entry to the XML file so that our new model will be copied. The Joomla!

framework will look for our model in the models directory, so the entry for this file will look like (it

should be added to the site section):

<filename>models/hello.php</filename>

Our new hello.xml file will look like:




<name>Hello</name>






















<filename>models/index.html</filename>


</files>

<administration>






in this section are copied from /admin/ in the package -->





</files>

</administration>

</install>

Conclusion

We now have a simple MVC component. Each element is very simple at this point, but provides a

great deal of flexibility and power.

Contributors

staalanden

Download


Developing a Model-View-Controller Component - Part 3 - Using the Database

Introduction


In the first two tutorials, we showed you how to build a simple model-view-controller component.

We had one view which retrieved data from a model (which was created in the 2nd tutorial). In this

tutorial, we will be working with the model. Instead of the data being hard coded in the model, the

model will retrieve the data from a table in the database.

This tutorial will demonstrate how to use the JDatabase class to retrieve data from the database.

Retrieving the Data

Our model currently has one method: getGreeting(). This method is very simple - all it does is

return the hard-coded greeting.

To make things more interesting, we will load the greeting from a database table. We will

demonstrate later how to create an SQL file and add the appropriate code to the XML manifest file

so that the table and some sample data will be created when the component is installed. For now,

we will simply replace our return statement with some code that will retrieve the greeting from the

database and return it.

The first step is to obtain a reference to a database object. Since Joomla! uses the database for its

normal operation, a database connection already exists; therefore, it is not necessary to create

your own. A reference to the existing database can be obtained using:

$db =& JFactory::getDBO();

JFactory is a static class that is used to retrieve references to many of the system objects. More

information about this class can be found in the API documentation.

The method name (getDBO) stands for get DataBase Object, and is easy and important to

remember.

Now that we have obtained a reference to the database object, we can retrieve our data. We do this

in two steps: * store our query in the database object

load the result

Our new getGreeting() method will therefore look like:

function getGreeting()

{

$db =& JFactory::getDBO();

$query = 'SELECT greeting FROM #__hello';

$db->setQuery( $query );

$greeting = $db->loadResult();

return $greeting;

}

hello is the name of the table that we will create later, and greeting is the name of the field that

stores the greetings. If you are not familiar with SQL, it would be helpful to take a tutorial or a

lesson to get yourself up to speed. One such tutorial can be found at w3schools.

The $db→loadResult() method will execute the stored database query and return the first field of

the first row of the result. See JDatabase API reference for more information about other load

methods in the JDatabase class.

Creating the Installation SQL File

The Joomla! installer has built-in support for executing queries during component installation. These

queries are all stored in a standard text file.

We will have three queries in our install file: the first will drop the table in case it already exists, the

second will create the table with the appropriate fields, and the third will insert the data.

Here are our queries:

DROP TABLE IF EXISTS `#__hello`;

CREATE TABLE `#__hello` (

`id` int(11) NOT NULL auto_increment,

`greeting` varchar(25) NOT NULL,

PRIMARY KEY (`id`)

) ENGINE=MyISAM AUTO_INCREMENT DEFAULT CHARSET=utf8;

INSERT INTO `#__hello` (`greeting`) VALUES ('Hello, World!'),

('Bonjour, Monde!'),

('Ciao, Mondo!');

You might find the prefix on the table names rather odd. Joomla! will replace this prefix with the

prefix used by the current install. For most installs, this table will become jos_hello. This allows

multiple installs of Joomla! to use the same database, and prevents collisions with other

applications using the same table names (i.e. two applications might share a database, but might

both require a ‘users’ table. This convention avoids problems.)

We have specified two fields in our database. The first field is id, and is called the ‘primary key’. The

primary key of a database table is a field that is used to uniquely identify a record. This is often

used to lookup rows in the database. The other field is greeting. This is the field that stores the

greeting that is returned from the query that we used above.

We will save our queries in a file called install.utf.sql.

Creating the Uninstall SQL File

Though we might hope that people will never want to uninstall our component, it is important that if

they do, we don’t leave anything behind. Joomla! will look after deleting the files and directories

that were created during install, but you must manually include queries that will remove and tables

that have been added to the database. Since we have only created one table, we only need one

query:

http://dev.joomla.org/component/option,com_jd-wiki/Itemid,/id,references:joomla.framework:database:jdatabase/

http://www.w3schools.com/sql/default.asp

DROP TABLE IF EXISTS `#__hello`;

We will save this query in a file called uninstall.utf.sql.

Updating our Install File

We need to change a few things in our install file. First, we need to add our two new files to the list

of files to install. SQL install file have to go in the admin directory. Second, we need to tell the

installer to execute the queries in our files on install and uninstall.

Our new file looks like this:




<name>Hello</name>























</files>

<install>

<sql>

<file charset="utf8" driver="mysql">install.sql</file>

</sql>

</install>

<uninstall>

<sql>

<file charset="utf8" driver="mysql">uninstall.sql</file>

</sql>

</uninstall>

<administration>






in this section are copied from /admin/ in the package -->





<filename>install.sql</filename>

<filename>uninstall.sql</filename>

</files>

</administration>

</install>

You will notice two attributes present on the <file> tags within the <install> and <uninstall>

sections: charset and driver. The charset is the type of charset to use. The only valid charset is utf8.

If you want to create install files for non-utf8 databases (for older version of MySQL), you should

omit this attribute.

The driver attribute specifies which database the queries were written for. Currently, this can only

be mysql, but in future versions of Joomla! there may be more database drivers available.

Conclusion

We now have a component that takes advantage of both the Joomla! MVC framework classes and

the JDatabase classes. You are now able to write MVC components that interact with the database

and can use the Joomla! installer to create and populate database tables.

Contributors

staalanden

Download



Developing a Model-View-Controller Component - Part 4 - Creating an Administrator Interface

Introduction

In the first three tutorials, we have developed a MVC component that retrieves its data from a table

in the database. Currently, there is no way to add data to the database except to do it manually

using another tool. In this tutorial, we will develop an administrator section for our component

which will make it possible to manage the entries in the database.

Creating the Basic Framework

The basic framework of the administrator panel is very similar to the site portion. The main entry

point for the administrator section of the component is admin.hello.php. This file is identical to the

hello.php file that was used in the site portion except the name of the controller it loads will be

changed to HellosController. The default controller is also called controller.php and this file is

identical to the default controller in the site portion, with the exception that the controller is named

HellosController instead of HelloController. This difference is so that JController will by default load

the hellos view, which will display a list of our greetings.

Here is the listing for admin.hello.php:

<?php

/**



* @link

http://dev.joomla.org/component/option,com_jd-wiki/Itemid,31/id,tutorials:components/

* @license GNU/GPL

*/

// no direct 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

$classname = 'HellosController'.$controller;

$controller = new $classname( );

// Perform the Request task

$controller->execute( JRequest::getVar( 'task' ) );

// Redirect if set by the controller

$controller->redirect();

?>

The view and model that we will start with is the hellos view and the hellos model. We will start with

the model.

The Hellos Model

The Hellos Model will be very simple. The only operation that we currently need is the ability to

retrieve the list of hellos from the database. This operation will be implemented in a method called

getData().

The JModel class has a built in protected method called _getList(). This method can be used to

simplify the task of retrieving a list of records from the database. We simply need to pass it the

query and it will return the list of records.

At a later point in time, we might want to use our query from within another method. Therefore, we

will create a private method called _buildQuery() which will return the query that will be passed to

_getList(). This makes it easier to change the query as well since it is localized in one place.

Therefore we need two methods in our class: getData() and _buildQuery().

_buildQuery() simply returns the query. It looks like:

/**

* Returns the query

* @return string The query to be used to retrieve the rows from the database

*/

function _buildQuery()

{

$query = ' SELECT * '

. ' FROM #__hello '

;

return $query;

}

getData() will obtain the query and retrieve the records from the database. Now it might happen

that we need to retrieve this list of data twice in one page load. It would be a waste to have to

query the database twice. Therefore, we will have this method store the data in a protected

property so that on subsequent requests it can simply return the data it has already retrieved. This

property will be called _data.

Here is the getData() method:

/**

* Retrieves the hello data

* @return array Array of objects containing the data from the database

*/

function getData()

{

// Lets load the data if it doesn't already exist

if (empty( $this->_data ))

{

$query = $this->_buildQuery();

$this->_data = $this->_getList( $query );

}

return $this->_data;

}

The completed model looks like:

<?php

/**

* Hellos Model for Hello World Component

*



* @link


* @license GNU/GPL

*/



jimport( 'joomla.application.component.model' );

/**

* Hello Model

*



*/

class HellosModelHellos extends JModel

{

/**

* Hellos data array

*

* @var array

*/

var $_data;

/**

* Returns the query

* @return string The query to be used to retrieve the rows from the database

*/

function _buildQuery()

{

$query = ' SELECT * '

. ' FROM #__hello '

;

return $query;

}

/**

* Retrieves the hello data

* @return array Array of objects containing the data from the database

*/

function getData()

{

// Lets load the data if it doesn't already exist

if (empty( $this->_data ))

{

$query = $this->_buildQuery();

$this->_data = $this->_getList( $query );

}


}

}

This file is saved as models/hellos.php.

The Hellos View

Now that we have a model to retrieve our data, we need to display it. This view will be fairly similar

to the view from the site section as well.

Just as our model was automatically instantiated in the site, so it is in the administrator. Methods

that start with get in the model can be accessed using the get() method of the JView class. So our

view has three lines: one to retrieve the data from the model, one to push the data into the

template, and one to invoke the display method to display the output. Thus we have:

<?php

/**

* Hellos View for Hello World Component

*



* @link


* @license GNU/GPL

*/



jimport( 'joomla.application.component.view' );

/**

* Hellos View

*



*/

class HellosViewHellos extends JView

{

/**

* Hellos view display method

* @return void

**/


{

JToolBarHelper::title( JText::_( 'Hello Manager' ), 'generic.png' );

JToolBarHelper::deleteList();

JToolBarHelper::editListX();

JToolBarHelper::addNewX();

// Get data from the model

$items =& $this->get( 'Data');

$this->assignRef( 'items', $items );


}

}

This file is saved as views/hellos/view.html.php.

The Hellos Template

The template will take the data pushed into it from the view and produce the output. We will

display our output in a simple table. While the frontend template was very simple, in the

administrator we will need a minimal amount of extra logic to handle looping through the data.

Here is our template:

<?php defined('_JEXEC') or die('Restricted access'); ?>

<form action="index.php" method="post" name="adminForm">

<div id="editcell">

<table class="adminlist">

<thead>

<tr>

<th width="5">

<?php echo JText::_( 'ID' ); ?>

</th>

<th>

<?php echo JText::_( 'Greeting' ); ?>

</th>

</tr>

</thead>

<?php

$k = 0;

for ($i=0, $n=count( $this->items ); $i < $n; $i++)

{

$row =& $this->items[$i];

?>

<tr class="<?php echo "row$k"; ?>">

<td>

<?php echo $row->id; ?>

</td>

<td>

<?php echo $row->greeting; ?>

</td>

</tr>

<?php

$k = 1 - $k;

}

?>

</table>

</div>

<input type="hidden" name="option" value="com_hello" />

<input type="hidden" name="task" value="" />

<input type="hidden" name="boxchecked" value="0" />

<input type="hidden" name="controller" value="hello" />

</form>

This template is saved as views/hellos/tmpl/default.php.

You will notice that our output is enclosed in a form. Though this is not necessary now, it will be

soon.

We have now completed the basic part of the first view. We have added five files to the admin

section of our component:

admin.hello.php

controller.php

models/hellos.php

views/hellos/view.html.php

views/hellos/tmpl/default.php

You can now add these files to the XML install file and give it a try!

Adding Functionality

So far our administrator section is pretty useless. It doesn’t really do anything - all it does is display

the entries that we have in our database.

In order to make it useful, we need to add some buttons and links.

The Toolbar

You may have noticed the toolbar that appears at the top of other Joomla! component administrator

panels. Our component needs one as well. Joomla! makes this very easy to do. We will add buttons

Delete records, Edit records, and create New records. We will also add a title that will be displayed

on our toolbar.

This is done by adding code to the view. To add the buttons, we use static methods from the

Joomla! JToolBarHelper class. The code looks like:

JToolBarHelper::title( JText::_( 'Hello Manager' ), 'generic.png' );

JToolBarHelper::deleteList();

JToolBarHelper::editListX();

JToolBarHelper::addNewX();

These three methods will create the appropriate buttons. The deleteList() method can optionally

take up to three parameters - the first parameter is a string to display to the user to confirm that

they want to delete the records. The second is the task that should be sent with the query (the

default is ‘remove’), and the third is the text that should be displayed below the button.

The editListX() and addNewX() methods can each take two optional parameters. The first is the task

(which are by default edit and add, respectively), and the second is the text that should be

displayed below the button.

*You may have noticed the use of the JText::_ method in the template before

and here as well. This is a handy function that makes component translation

much easier. The JText::_ method will look up the string in your component

language file and return the translated string. If not translation is

found, it will return the string that you passed it. If you want to

translate your component into another language, all you have to do is

create a language file that will map the strings within the quotes to the

translated version of the string.

Checkboxes and Links

We now have buttons. Two of those buttons operate on existing records. But how do we know

which records to operate on? We have to let the user tell us. To do this, we need to add checkboxes

to our table so that the user can select certain records. This is done in our template.

In order to the add the checkboxes, we need to add an extra column into our table. We will add the

column in between the two that we already have.

In the header of the column, we will add a checkbox which can be used to toggle all the boxes

below it on or off:

<th width="20">

<input type="checkbox" name="toggle" value="" onclick="checkAll(<?php echo count(

$this->items ); ?>);" />

</th>

The Javascript checkAll function is a function that is built into the Joomla! base Javascript package

that provides the functionality that we want here.

Now we need to add the checkboxes into the individual rows. Joomla!’s JHTML class has a method,

JHTML::_(), which will generate our checkbox for us. We will add the following line to our loop:

$checked = JHTML::_( 'grid.id', $i, $row->id );

after the line:


Then we will add a cell in between the two that we already have:

<td>

<?php echo $checked; ?>

</td>

It can be cumbersome to have to check the box that we want to edit and then move up and click

the edit button. Therefore, we will add a link that it will go straight to the greeting’s edit form. We

will add the following line after the call to the JHTML::_() method to generate the link HTML:

$link = JRoute::_( 'index.php?option=com_hello>controller=hello>task=edit>cid[]='. $row-

>id );

And we include the link in the cell showing the greeting text:

<td>

<a href="<?php echo $link; ?>"><?php echo $row->greeting; ?></a>

</td>

You will notice that this link points to the hello controller. This controller will handle the data

manipulation of our greetings.

If you recall from above, we had four hidden input fields at the bottom of our form. The first input

field was named ‘option’. This field is necessary so that we stay in our component. The second

input field was task. This form property gets set when one of the buttons in the toolbar is clicked. A

Javascript error will result and the buttons will not work if this input field is omitted. The third input

field is the boxchecked field. This field keeps track of the number of boxes that are checked. The

edit and delete buttons will check to ensure that this is greater than zero and will not allow the form

to be submitted if it is not. The fourth input field is the controller field. This is used to specify that

tasks fired from this form will be handled by the hello controller.

Here is the code for the completed default.php file:


<form action="index.php" method="post" name="adminForm">

<div id="editcell">

<table class="adminlist">

<thead>

<tr>

<th width="5">

<?php echo JText::_( 'ID' ); ?>

</th>

<th>

<?php echo JText::_( 'Greeting' ); ?>

</th>

</tr>

</thead>

<?php

$k = 0;

for ($i=0, $n=count( $this->items ); $i < $n; $i++)

{


?>

<tr class="<?php echo "row$k"; ?>">

<td>

<?php echo $row->id; ?>

</td>

<td>

<?php echo $row->greeting; ?>

</td>

</tr>

<?php

$k = 1 - $k;

}

?>

</table>

</div>



<input type="hidden" name="boxchecked" value="0" />


</form>

Our hellos view is now complete. You can try out the component now to see the results.

The component can be downloaded at: com_hello4a.zip

Getting Down and Dirty: Doing the Real Work

Now that the Hellos view is done, it is time to move to the Hello view and model. This is where the

real work will get done.

The Hello Controller

http://dev.joomla.org/components/com_jd-wiki/data/media/components/com_hello4a.zip

Our default controller just isn’t going to cut it when it comes to doing work - all it is capable of doing

is displaying views.

We need to be able to handle the tasks that we are launching from the Hellos view: add, edit and

remove.

Add and edit are essentially the same task: they both display a form to the user that allows a

greeting to be edited. The only difference is that new displays a blank form, and edit displays a

form with data already in it. Since they are similar, we will map the add task onto the edit task

handler. This is specified in our constructor:

/**

* constructor (registers additional tasks to methods)

* @return void

*/

function __construct()

{

parent::__construct();

// Register Extra tasks

$this->registerTask( 'add' , 'edit' );

}

The first parameter of JController::registerTask is the task to map, and the second is the method to

map it to.

We will start with handling the edit task. The controller’s job is fairly simple for the edit task. All it

has to do is specify the view and layout to load (the hello view and the form layout). We will also tell

Joomla! to disable the mainmenu while we are editing our greeting. This prevents users from

leaving unsaved records open.

Our edit task handler looks like:

/**

* display the edit form

* @return void

*/

function edit()

{

JRequest::setVar( 'view', 'hello' );

JRequest::setVar( 'layout', 'form' );

JRequest::setVar('hidemainmenu', 1);

parent::display();

}

The Hello View

The Hello view will display a form which will allow the user to edit a greeting. The display method if

the hello view has to do a few simple tasks:

retrieve the data from the model

create the toolbar

pass the data into the template

invoke the display() method to render the template

This becomes a bit more complicated because the one view handles both the edit and add tasks. In

our toolbar we want the user to know what whether they are adding or editing, so we have to

determine which task was fired.

Since we are already retrieving the record that we want to display from the model, we can use this

data to determine what task was fired. If the task was edit, then the id field of our record will have

been set. If the task was new, then it will not have been set. This can be used to determine if we

have a new record or an existing record.

We will add two buttons to the toolbar: save and cancel. Though the functionality will be the same,

we want to display different buttons depending on whether it is a new or existing record. If it is a

new record, we will display cancel. If it already exists, we will display close.

Thus our display method looks like this:

/**

* display method of Hello view

* @return void

**/


{

//get the hello

$hello =& $this->get('Data');

$isNew = ($hello->id < 1);

$text = $isNew ? JText::_( 'New' ) : JText::_( 'Edit' );

JToolBarHelper::title( JText::_( 'Hello' ).': <small><small>[ ' . $text.'

]</small></small>' );

JToolBarHelper::save();

if ($isNew) {

JToolBarHelper::cancel();

} else {

// for existing items the button is renamed `close`

JToolBarHelper::cancel( 'cancel', 'Close' );

}

$this->assignRef('hello', $hello);


}

The Hello Model

Our view needs data. Therefore, we need to create a model to model a hello.

Our model will have two properties: _id and _data. _id will hold the id of the greeting and data will

hold the data.

We will start with a constructor, which will attempt to retrieve the id from the query:

/**

* Constructor that retrieves the ID from the request

*

* @access public

* @return void

*/

function __construct()

{

parent::__construct();

$array = JRequest::getVar('cid', 0, '', 'array');

$this->setId((int)$array[0]);

}

The JRequest::getVar() method is used to retrieve data from the request. The first parameter is the

name of the form variable. The second parameter is the default value to assign if there is no value

found. The third parameter is the name of the hash to retrieve the value from (get, post, etc), and

the last value is the data type that should be forced on the value.

Our constructor will take the first value from the cid array and assign it to the id.

Our setId() method can be used to set our id. Changing the id that our model points to will mean

the id points to the wrong data. Therefore, when we set the id, we will clear the data property:

/**

* Method to set the hello identifier

*

* @access public

* @param int Hello identifier

* @return void

*/

function setId($id)

{

// Set id and wipe data

$this->_id = $id;

$this->_data = null;

}

Finally, we need a method to retrieve our data: getData()

getData will check if the _data property has already been set. If it has, it will simply return it.

Otherwise, it will load the data from the database.

/**

* Method to get a hello

* @return object with data

*/

function &getData()

{

// Load the data

if (empty( $this->_data )) {

$query = ' SELECT * FROM #__hello '.

' WHERE id = '.$this->_id;

$this->_db->setQuery( $query );

$this->_data = $this->_db->loadObject();

}

if (!$this->_data) {

$this->_data = new stdClass();

$this->_data->id = 0;

$this->_data->greeting = null;

}


}

The Form

Now all that is left is to create the form that the data will go into. Since we specified our layout as

form, the form will go in a file in the tmpl directory of the hello view called form.php:


<form action="index.php" method="post" name="adminForm" id="adminForm">

<div class="col100">

<fieldset class="adminform">

<legend><?php echo JText::_( 'Details' ); ?></legend>

<table class="admintable">

<tr>

<td width="100" align="right" class="key">

<label for="greeting">

<?php echo JText::_( 'Greeting' ); ?>:

</label>

</td>

<td>

<input class="text_area" type="text" name="greeting" id="greeting"

size="32" maxlength="250" value="<?php echo $this->hello->greeting;?>" />

</td>

</tr>

</table>

</fieldset>

</div>

<div class="clr"></div>


<input type="hidden" name="id" value="<?php echo $this->hello->id; ?>" />



</form>

Notice that in addition to the input field, there is a hidden field for the id. The user doesn’t need to

edit the id (and shouldn’t), so we silently pass it along in the form.

Implementing the Functionality

So far, our controller only handles two tasks: edit and new. However, we also have buttons to save,

delete and cancel records. We need to write code to handle and perform these tasks.

Saving a Record

The logical next step is to implement the functionality to save a record. Normally, this would require

some switches and logic to handle various cases, such as the difference between creating a new

record (an INSERT query), and updating an existing query (an UPDATE query). Also, there are

complexities involved in getting the data from the form and putting it into the query.

The Joomla! framework takes care of a lot of this for you. The JTable class makes it easy to

manipulate records in the database without having to worry about writing the SQL code that lies

behind these updates. It also makes it easy to transfer data from an HTML form into the database.

Creating the Table Class

The JTable class is an abstract class from which you can derive child classes to work with specific

tables. To use it, you simply create a class that extends the JTable class, add your database fields

as properties, and override the constructor to specify the name of the table and the primary key.

Here is our JTable class:

<?php

/**

* Hello World table class

*



* @link


* @license GNU/GPL

*/

// no direct access

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

/**

* Hello Table class

*



*/

class TableHello extends JTable

{

/**

* Primary Key

*

* @var int

*/

var $id = null;

/**

* @var string

*/

var $greeting = null;

/**

* Constructor

*

* @param object Database connector object

*/

function TableHello( &$db ) {

parent::__construct('#__hello', 'id', $db);

}

}

?>

You will see here that we have defined our two fields: the id field and the greeting field. Then we

have defined a constructor, which will call the constructor of the parent class and pass it the name

of the table (hello), the name of the field which is the primary key (id), and the database connector

object.

This file should be called hello.php and it will go in a directory called tables in the administrator

section of our component.

Implementing the Function in our Model

We are now ready to add the method to the model which will save our record. We will call this

method store. Our store() method will do three things: bind the data from the form to the

TableHello object, check to ensure that the record is properly formed, and store the record in the

database.

Our method looks like:

/**

* Method to store a record

*

* @access public

* @return boolean True on success

*/

function store()

{

$row =& $this->getTable();

$data = JRequest::get( 'post' );

// Bind the form fields to the hello table

if (!$row->bind($data)) {

$this->setError($this->_db->getErrorMsg());

return false;

}

// Make sure the hello record is valid

if (!$row->check()) {


return false;

}

// Store the web link table to the database

if (!$row->store()) {


return false;

}

return true;

}

This method gets added to the hello model.

The method takes one parameter, which is an associative array of data that we want to store in the

database. This can easily be retrieved from the request as will be seen later.

You will see that the first line retrieves a reference to our JTable object. If we name our table

properly, we don’t have to specify its name - the JModel class knows where to find it. You may recall

that we called our table class TableHello and put it in a file called hello.php in the tables directory. If

you follow this convention, the JModel class can create your object automatically.

The second line will retrieve the data from the form. The JRequest class makes this very easy. In

this case, we are retrieving all of the variables that were submitted using the ‘POST’ method. These

will be returned as an associative array.

The rest is easy - we bind, check and store. The bind() method will copy values from the array into

the corresponding property of the table object. In this case, it will take the values of id and greeting

and copy them to our TableHello object.

The check() method will perform data verification. In the JTable() class, this method simply returns

true. While this doesn’t provide any value for us currently, by calling this method we make it

possible to do data checking using our TableHello class in the future. This method can be

overridden in our TableHello class with a method that performs the appropriate checks.

The store() method will take the data that is in the object and store it in the database. If the id is 0,

it will create a new record (INSERT), otherwise, it will update the existing record (UPDATE).

Adding the Task to the Controller

We are now ready to add our task to the controller. Since the task that we are firing is called ‘save’,

we must call our method ‘save’. This is simple:

/**

* save a record (and redirect to main page)

* @return void

*/

function save()

{

$model = $this->getModel('hello');

if ($model->store()) {

$msg = JText::_( 'Greeting Saved!' );

} else {

$msg = JText::_( 'Error Saving Greeting' );

}

// Check the table in so it can be edited.... we are done with it anyway

$link = 'index.php?option=com_hello';

$this->setRedirect($link, $msg);

}

All we do is get our model and invoke the store() method. Then we use the setRedirect() method to

redirect back to our list of greetings. We also pass a message along, which will be displayed at the

top of the page.

frame|none|The message that was passed is displayed at the top of the page.

Deleting a Record

Implementing the Function in the Model

In the model, we will retrieve the list of IDs to delete and call the JTable class to delete them. Here

it is:

/**

* Method to delete record(s)

*

* @access public

* @return boolean True on success

*/

function delete()

{

$cids = JRequest::getVar( 'cid', array(0), 'post', 'array' );

$row =& $this->getTable();

foreach($cids as $cid) {

if (!$row->delete( $cid )) {

$this->setError( $row->getErrorMsg() );

return false;

}

}

return true;

}

We invoke the JRequest::getVar() method to get the data from the request, then we invoke the

$row→delete() method to delete each row. By storing errors in the model we make it possible to

retrieve them later if we so choose.

Handling the Remove Task in the Controller

This is similar to the save() method which handled the save task:

/**

* remove record(s)

* @return void

*/

function remove()

{

$model = $this->getModel('hello');

http://dev.joomla.org/component/option,com_jd-wiki/Itemid,/id,image:message.png/

if(!$model->delete()) {

$msg = JText::_( 'Error: One or More Greetings Could not be Deleted' );

} else {

$msg = JText::_( 'Greeting(s) Deleted' );

}

$this->setRedirect( 'index.php?option=com_hello', $msg );

}

Cancelling the Edit Operation

To cancel the edit operation, all we have to do is redirect back to the main view:

/**

* cancel editing a record

* @return void

*/

function cancel()

{

$msg = JText::_( 'Operation Cancelled' );

$this->setRedirect( 'index.php?option=com_hello', $msg );

}

Conclusion

We have now implemented a basic backend to our component. We are now able to edit the entries

that are viewed in the frontend. We have demonstrated the interaction between models, views and

controllers. We have shown how the JTable class can be extended to provide easy access to tables

in the database. It can also be seen how the JToolBarHelper class can be used to create button bars

in components to present a standardized look between components.

Contributors

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