Topic 4 – Part 2: Magento Object Relational Mapping (ORM)

• Convert different types of data to objects
• Convert objects to various types of data

2. ORM in Magento

In Magento, ORM is shown as Models (in Magento design pattern MVC). Most of the models are inherited from the Varien_Object class, along with using PHP magic _get and _set functions to set and retrieve the data of the object:

$product = Mage::getModel(‘catalog/product’)->setPrice(100);
echo $product->getPrice();

Models in Magento are divided into 3 types:

• Models working with incoherent data: The typical example for this type is adminhtml/system_config_source_yesno model with the content below:

class Mage_Adminhtml_Model_System_Config_Source_Yesno
{
    public function toOptionArray(){
        return array(
            array('value' => 1, 'label'=>Mage::helper('adminhtml')->__('Yes')),
            array('value' => 0, 'label'=>Mage::helper('adminhtml')->__('No')),
        );
    }
}

Data that this type of models works with is 0/1 value and Yes/No label. The model doesn’t get data from the database and doesn’t write data in the database as well.

public function loadBase(){
        $etcDir = $this->getOptions()->getEtcDir();
        $files = glob($etcDir.DS.'*.xml');
        $this->loadFile(current($files));
        while ($file = next($files)) {
            $merge = clone $this->_prototype;
            $merge->loadFile($file);
            $this->extend($merge);
        }
        if (in_array($etcDir.DS.'local.xml', $files)) {
            $this->_isLocalConfigLoaded = true;
        }
        return $this;
    }

The model working with XML database converts the data stored by XML configuration file to working objects. There are separated methods to work with theXML database like getNode, getSectionNode…

• Models working with SQL database: take and write data in the database through the SQL structure query demand. The responsibility of these models is to change actions to the data query demands.

• Models working with one database table (such as core/website model). This model works with one table in database. Loading or saving the data will just relate to this table. For instance:

$website = Mage::getModel(‘core/website’)->load(0);
$website->setId(1)->save();

• Models working with multi – database table: work with EVA database. For example: catalog/product model. In this case, loading or saving data will be relevant to a set of table. This model has to map the data of multi-table to its object. The data query will be implemented during using this model.

$product = Mage::getModel(‘catalog/product’)->load(1);
$product->setId(2)->save();

That’s all for today. I hope you’ve enjoyed my tutorial and find it helpful. See you again in the next posts.