Design Patterns

Factory:

It implement the concept of factories and deals with the problem of creating objects without specifying the exact class of object that will be created.

1	$product = Mage::getModel(‘catalog/product’);

Singleton:

It restricts the instantiation of a class to one object. It will refer to same object each time called.

1	$category = Mage::getSingleton(‘catalog/session’);

Registry:

It is a way to store information throughout your application.

1 2	Mage::register(‘key’,$value); //stores $currentCategory = Mage::registry(‘key’); //retrives

Prototype:

It determines the type of object to create. In Magento it can be Simple, Configurable, Grouped, Bundle, Downloadable or Virtual types.

1	Mage:getModel(‘catalog/product’)->getTypeInstance();

Observer:

It is mainly used to implement distributed event handling systems. Here the subject maintains a list of its dependents, called observers, and notifies them automatically of any state changes, usually by calling one of their methods.

1	Mage::dispatchEvent(‘event_name’, array(‘key’=>$value));

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<config>     <global>         <events>             <event_name>                 <observers>                     <unique_name>                         <class>Class_Name</class>                         <method>methodName</method>                     </unique_name>                 </observers>             </event_name>         </events>     </global> </config>

Object Pool:

It is used to reuse and share objects that are expensive to create.

1 2	$id = Mage::objects()->save($object); $object = Mage::objects($id);

Iterator:

It is used to traverse a collection and access the collection’s items.

1	Mage::getModel(‘catalog/product’)->getCollection();

Lazy Loading:

It is used to defer initialization of an object until the point at which it is needed.

1 2	$collection_of_products = Mage::getModel(‘catalog/product’) ->getCollection();

Decorator:

It is used to extend or modify the behaviour of an object at runtime.

1	<script type=”text/javascript”>decorateTable(‘product_comparison’);</script>

Helper:

Multiple methods are available for use by other objects. Here you can use core’s helper methods from anywhere in the application.

1	Mage::helper(‘core’);

Service Locator:

Allows overrides or renamed physical resources (e.g. Classes, DB tables, etc)

1	Mage::getModel(‘catalog/product’) and $installer->getTable(‘customer/address_entity’);

Null object

Provide an object as a surrogate for the lack of an object of a given type. / The Null Object Pattern provides intelligent do nothing behavior, hiding the details from its collaborators.

1	$collection->getFirstItem();