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Mastering Joomla! 1.5 Extension and Framework Development
1849510520, 9781849510523

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Some Data

APIs and Web Services

The irst line of code is known as the XML declaration. It declares that the document is XML, which version of XML it is, and what the character encoding is. We then encounter the opening tag rootNode. XML documents have one root node that encapsulates the XML document. Within rootNode is another node, subNode. This node contains some data and an attribute called attr. There is no limit to the depth of an XML document; this is one of the things that make XML so lexible. When creating our own XML schemas, we can choose the names of all the tags and attributes that we are going to implement. Here are some quick pointers that should help when we come to deine and write our own XML documents: •

Tag and attribute names are case sensitive

•

Tag and attribute names can only contain letters and numbers

•

Special characters within data must be encoded

•

Tags must be nested correctly

•

Attribute values must be encapsulated in double quotes

In order to illustrate how we might use XML data we will add a simple layout to the frontend com_boxoffice component revue view. We will create the /views/revue/ tmpl/xml.php ile, modify the /views/revue/view.html.php ile, and add a menu item to the main menu to display the view. Let's begin by modifying the view.html.php ile to handle the new view. Look for the following line: if( $this->getLayout() == 'list' )

Replace it with the following: if( $this->getLayout() == 'xml' ) { // Fall through and display the xml layout } else if( $this->getLayout() == 'list' )

Save the view.html.php ile. Now the view can output the XML layout as well as the list and individual revue layouts. In order to test our new layout we will need to add a new menu item using the administrator Menu Manager, but that must wait until after we have created the XML layout.

[ 332 ]

Chapter 10

So let's create the xml.php layout ile and begin by add the following code:

Moving Pictures Rush 1981

Tom Sawyer Red Barchetta YYZ Limelight The Camera Eye [ 333 ]

Chapter 10

Next we use the attributes() method. This method returns the value of an attribute from the current node. When we use this method we supply the name of the attribute we wish to retrieve, in this case name. If a requested attribute does not exist, null is returned. If we wish to retrieve all of the attributes associated with a node, we simply do not pass the name of an attribute. This returns an associative array of the node's attributes. If the root node is not of the expected type we can use the name() method to determine the name of the node type; in our case we are checking for a catalog node: if ($document->name() != 'catalog') { // handle invalid root node }

Nodes can have child nodes; in our example the root node has one child node, album. The root node could contain additional album nodes. To retrieve child nodes we use the children() method. This method returns an array of nodes, each of which is a JSimpleXMLElement object: $children = $document->children();

There may also be a combination of album and single nodes. A single node would be essentially identical to the album node, except it would contain data speciically for music released as a single. We could use the $children array and determine the type of each node using the name() method. This is a bit cumbersome and for larger XML iles rather process intensive. Luckily for us, the child nodes are categorized into types. These are accessible through attributes that are named after the node type. So, in order to retrieve the album nodes from the root node we add this to our layout: $albums =& $xmldoc->album;

Our next task is to process the $albums array. As we iterate over the array, we will have to access the sub-nodes: name, artist, year, and tracks. Although we could use a method similar to what we used before, there is another way. We can use the getElementByPath() method to retrieve a node, as long as its path is unique. Since an album will only ever have one of each of these sub-nodes we can use this approach.

[ 335 ]

APIs and Web Services

This example iterates over the $albums array and outputs title, artist, and year (we will deal with tracks shortly): // Output the albums echo 'Albums'; for ($i = 0, $c = count($albums); $i < $c; $i ++ ) { // get the album $album =& $albums[$i]; echo ''; if ($name =& $album->getElementByPath('title')) { // display title echo ''.$name->data().'
'; } if ($artist =& $album->getElementByPath('artist')) { // display the artist echo ''.$artist->data().''; } if ($year =& $album->getElementByPath('year')) { // display the year of release echo ' ('.$year->data().')'; } }

Our use of the getElementByPath() method should be clear; we simply pass the name of the child node. For deeper paths we simply add forward slashes to separate the node names (for example node/node/node). Another method that we used is the data() method. This method returns any data that is contained within a node. Remember that the getElementByPath() method returns JSimpleXMLElement objects, and title, artist, and year are nodes in their own right. We are now left with one last thing to do. We need to get the track listing for each album. To do this, we will iterate over the tracks child nodes: if ($tracks =& $album->getElementByPath('tracks')) { // get the track listing $listing =& $tracks->track;

[ 336 ]

Chapter 10 // output listing table echo ''; for ($ti = 0, $tc = count($listing); $ti < $tc; $ti ++) { // output an individual track $track =& $listing[$ti]; echo ''; echo ''; echo ''; echo ''; } echo '

Track	Length
'.$track->data().'	'.$track->attributes('length').'

'; } echo '';

We retrieve the tracks node using getElementByPath(). We get each track using the track attribute. We get the name of the track using the data() method. We get the track length attribute using the attributes() method. We can use this example in conjunction with the previous example in order to output each album and its track listing. The next screenshot demonstrates what the output could look like once some CSS has been applied:

[ 337 ]

APIs and Web Services

Editing In addition to interrogating XML data, we can modify data. To add a new album to the catalog we use the addChild() method; this method adds a new sub-node of a speciied type and returns a reference to the new node. For our purposes, let's add the following to our layout ile immediately following $xmldoc =& $parser->document; $newAlbum =& $document->addChild('album');

Once we have added the new album node, we must add the child nodes title, artist, year, and tracks: $title $artist $year $tracks

=& =& =& =&

$newAlbum->addChild('title'); $newAlbum->addChild('artist'); $newAlbum->addChild('year'); $newAlbum->addChild('tracks');

The irst three nodes require us to set data values, however we cannot do this when we create the node; we must do this afterwards using the setData() method: $title->setData('Green Onions'); $artist->setData('Booker T. & The MG\'s'); $year->setData('1962');

The tracks node requires a bit more effort since we must add multiple track nodes to this node, each of which needs to include the track length as a parameter: $track =& $tracks->addChild('track', array('length'=>'1.45')); $track->setData('Green Onions');

The second parameter that we pass to the addChild() method is an associative array of node parameters. In this case we specify the length of the track as 1.45. We then proceed to set the name of the track using the setData() method. There is another way in which we could have added the length parameter to the track node. The addAttribute() method is used to add and modify attributes. Suppose that we accidentally entered the wrong length value and we now wish to correct it: $track->addAttribute('length', '2.45');

[ 338 ]

Chapter 10

Before we start, we need to consider the data we are going to retrieve. We will work with our #__boxoffice_revues table and use our revue model to retrieve a single record from the table. We will modify the view.xml.php ile that we created in Chapter 5, Component Design in the revue view but irst we will make a copy of it and name it view.raw.php. We are essentially going to replace the display() method of the BoxofficeViewRevue class. To begin we need to retrieve the speciied record from the table: function display( $tpl = null ) { // Get the model $model =& $this->getModel(); // Get the cid array from the default request hash // If no cid array in the request, check for id $cid = JRequest::getVar('cid', null, 'DEFAULT', 'array'); $id = $cid ? $cid[0] : JRequest::getInt( 'id', 0 ); $revue =

$model->getRevue( $id );

This retrieves the data from the revue model using the getRevue() method. After retrieving the data we build the XML response using the JSimpleXMLElement class: // get JSimpleXMLElement class jimport('joomla.utilities.simplexml'); // create root node with attibute of id $xml = new JSimpleXMLElement('film', array('id' => $revue->id));

This creates a root node of type revue with an attribute id with the value of the chosen item's ID. Next, we add sub-nodes: // add elements to the XML $title =& $xml->addChild('title'); $revuer =& $xml->addChild('revuer'); $stars =& $xml->addChild('stars'); $text =& $xml->addChild('revue'); // set element data $title->setData($revue->title); $revuer->setData($revue->revuer); $stars->setData($revue->stars); $text->setData($revue->revue); [ 341 ]

APIs and Web Services

This adds four sub-nodes and populates them with the record's corresponding values. Our inal task is to output the XML. We start with the XML declaration and then use the toString() method: echo ''."\n"; echo $xml->toString();

If we were to test this now, our response would be displayed as plain text. Although we have declared the content as XML, we have not declared the document header MIME type as text/xml. To do this we use the document setMimeEncoding() method: $document =& JFactory::getDocument(); $document->setMimeEncoding('text/xml');

We are now almost ready to take a look at our XML response. We can do this by simply adding the string &format=xml to the end or our URI query string when viewing a single revue. This tells Joomla! that we want to use the RAW document and that we want to use the view class held in the view.xml.php ile. But before we can do this we must make a small modiication to the /com_boxoffice/ controller.php ile. The existing display() method does not handle different formats, so we must add one line and change another, as follows: function display() { // Set the view and the model $view = JRequest::getVar( 'view', 'revue' ); $layout = JRequest::getVar( 'layout', 'default' ); $format = JRequest::getVar( 'format', 'html' ); $view =& $this->getView( $view, $format ); $model =& $this->getModel( 'revue' ); $view->setModel( $model, true ); $view->setLayout( $layout ); // Display the revue $view->display(); }

[ 342 ]

APIs and Web Services

Update Area

We place a div element with the id of update immediately following the form; this will be where the results from the AJAX request will be displayed. Save the ile and append /index.php?option=com_boxoffice&cid[]=1l&layout= raw to your site URL. You should be presented with the following output:

We will place a record id in the input ield which will become part of the request. However, before we can obtain the desired results we must add some JavaScript to handle the response. It's important when we add the JavaScript that we encapsulate it within the window domready event. This ensures that the JavaScript isn't executed until the DOM (Document Object Model) is fully loaded. Immediately after the code we just entered, we must add the following: