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<?php
/**
* Add extension that can be added to an object with {@link Object::add_extension()}.
* For {@link DataObject} extensions, use {@link DataExtension}.
* Each extension instance has an "owner" instance, accessible through
* {@link getOwner()}.
* Every object instance gets its own set of extension instances,
* meaning you can set parameters specific to the "owner instance"
* in new Extension instances.
*
* @package framework
* @subpackage core
*/
abstract class Extension {
/**
* This is used by extensions designed to be applied to controllers.
* It works the same way as {@link Controller::$allowed_actions}.
*/
private static $allowed_actions = null;
/**
* The object this extension is applied to.
*
* @var Object
*/
protected $owner;
/**
* The base class that this extension was applied to; $this->owner must be one of these
* @var DataObject
*/
protected $ownerBaseClass;
/**
* Reference counter to ensure that the owner isn't cleared until clearOwner() has
* been called as many times as setOwner()
*/
private $ownerRefs = 0;
public $class;
public function __construct() {
$this->class = get_class($this);
}
/**
* Called when this extension is added to a particular class
*
* @static
* @param $class
*/
public static function add_to_class($class, $extensionClass, $args = null) {
// NOP
}
/**
* Set the owner of this extension.
* @param Object $owner The owner object,
* @param string $ownerBaseClass The base class that the extension is applied to; this may be
* the class of owner, or it may be a parent. For example, if Versioned was applied to SiteTree,
* and then a Page object was instantiated, $owner would be a Page object, but $ownerBaseClass
* would be 'SiteTree'.
*/
public function setOwner($owner, $ownerBaseClass = null) {
if($owner) $this->ownerRefs++;
$this->owner = $owner;
if($ownerBaseClass) $this->ownerBaseClass = $ownerBaseClass;
else if(!$this->ownerBaseClass && $owner) $this->ownerBaseClass = $owner->class;
}
public function clearOwner() {
if($this->ownerRefs <= 0) user_error("clearOwner() called more than setOwner()", E_USER_WARNING);
$this->ownerRefs--;
if($this->ownerRefs == 0) $this->owner = null;
}
/**
* Returns the owner of this extension.
*
* @return Object
*/
public function getOwner() {
return $this->owner;
}
/**
* Helper method to strip eval'ed arguments from a string
* thats passed to {@link DataObject::$extensions} or
* {@link Object::add_extension()}.
*
* @param string $extensionStr E.g. "Versioned('Stage','Live')"
* @return string Extension classname, e.g. "Versioned"
*/
public static function get_classname_without_arguments($extensionStr) {
return (($p = strpos($extensionStr, '(')) !== false) ? substr($extensionStr, 0, $p) : $extensionStr;
}
}
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