PHP North East - Registry Design Pattern

Registry PatternThewith lazy loading goodnessMichael Peacock

whois michaelpeacock.co.ukExperienced senior / lead web developerWeb Systems Developer for SmithElectric Vehicles US CorpAuthor of 6 web development booksOwner / CTO of CentralAppsLimitedJust launched first beta product: invoicecentral.co.ukZend Certified Engineer

Commonly used objects and settings...Within Bespoke frameworks and large applications most of the code often needs access to core objects, settings and variables.

...such asDatabase Access / Abstraction layersTemplate enginesObject for the currently logged in userObjects which perform common tasks, such as email sending or data processingSite settings: path to uploads folder, cache folder, site URL, etc

The solution: RegistryCreate a registry to store these core objects and settingsProvide methods to store and retrieve these objects and settingsPass this object around your application (e.g. To your models and controllers) –or- make it a singleton (yuk)

Registry: basics<?php class Registry { private $objects = array(); private $settings = array(); public function __construct(){}public function storeObject( $object, $key ){} public function getObject( $key ){} public function storeSetting( $setting, $key ){} public function getSetting( $key ){} }?>

Registry: concept codepublic function storeObject( $object, $key ){ if( array_key_exists( $key, $this->objects ) ) { //throw an exception }elseif( is_object( $object ) ){ $this->objects[ $key ] = $object; }}public function getObject( $key ){ if( array_key_exists( $key, $this->objects ) && is_object( $this->objects[ $key ] ) ) { return $this->objects[ $key ]; } else { //throw an exception }}EASY!

Registry: usageMake your code awarePublic function __construct( Registry $registry){ $this->registry = $registry;}Store an object$this->registry->storeObject( $template, ‘template’ );Access your objects$this->registry->getObject(‘template’)->output();

Registry: The goodKeeps core objects and settings in one placeMakes it easy to access and use these objects and the data or functionality they hold withinCommon interface for storing, retrieving and managing common objects and settings

Registry: The badAll aspects of your application need to be registry aware... ...though its easy to simply pass the registry via the constructor to other parts of your codeWorks best with a front controller / single entry point to your application, otherwise you need to duplicate your registry setup throughout your code

Registry: The uglyBloat!If you rely on the registry too much, you end up with objects or settings which you only use some of the timeThis takes up additional resources, time and memory to setup and process the objects and settings for each page load, only for them to be used 50% of the time

Registry: de-uglificationMake the registry lazy loadingRegistry is aware of all of its objectsObjects are only instantiated and stored when they are first required, and not beforeRegistry knows about core settings/data that is used frequently, and knows how to access other data if/when required

De-uglification: Make the registry aware of its objects$defaultRegistryObjects = array(); $db = array( 'abstract' => 'database', 'folder' => 'database', 'file' => 'mysql.database', 'class' => 'MySQLDatabase', 'key' => 'db' ); $defaultRegistryObjects['db'] = $db; $template = array( 'abstract' => null, 'folder' => 'template', 'file' => 'template', 'class' => 'Template', 'key' => 'template' ); $defaultRegistryObjects['template'] = $template; $urlp = array( 'abstract' => null, 'folder' => 'urlprocessor', 'file' => 'urlprocessor', 'class' => 'URLProcessor', 'key' => 'urlprocessor' );

De-uglification If the object isn’t set, load it the lazy way/** * Get an object from the registry* - facilitates lazy loading, if we haven't used the object yet and it is part of the setup, then require and instantiate it! * @param String $key* @return Object */public function getObject( $key ) { if( in_array( $key, array_keys( $this->objects ) ) ) {return $this->objects[$key]; }elseif( in_array( $key, array_keys( $this->objectSetup ) ) ) { if( ! is_null( $this->objectSetup[ $key ]['abstract'] ) ) { require_once( FRAMEWORK_PATH . 'registry/aspects/' . $this->objectSetup[ $key ]['folder'] . '/' . $this->objectSetup[ $key ]['abstract'] .'.abstract.php' ); }require_once( FRAMEWORK_PATH . 'registry/aspects/' . $this->objectSetup[ $key ]['folder'] . '/' . $this->objectSetup[ $key ]['file'] . '.class.php' ); $o = new $this->objectSetup[ $key ]['class']( $this ); $this->storeObject( $o, $key ); return $o; }}

De-uglification: settingsApply the same approach to settings / dataQuery your core settingsIf the setting requested hasn’t been loaded, load all related settings (works best if you prefix your keys with a group name)

ConclusionEasily access your core objects, functionality and data from anywhere in your applicationApply some lazy loading to keep your application running leanEnjoy!

Any questions?www.michaelpeacock.co.ukwww.twitter.com/michaelpeacockwww.invoicecentral.co.uk

PHP North East - Registry Design Pattern

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PHP North East - Registry Design Pattern