1 <?php
 2 /**
 3  * Add extension that can be added to an object with {@link Object::add_extension()}.
 4  * For {@link DataObject} extensions, use {@link DataObjectDecorator}.
 5  * Each extension instance has an "owner" instance, accessible through
 6  * {@link getOwner()}.
 7  * Every object instance gets its own set of extension instances,
 8  * meaning you can set parameters specific to the "owner instance"
 9  * in new Extension instances.
10  *
11  * @package sapphire
12  * @subpackage core
13  */
14 abstract class Extension {
15     /**
16      * This is used by extensions designed to be applied to controllers.
17      * It works the same way as {@link Controller::$allowed_actions}.
18      */
19     public static $allowed_actions = null;
20 
21     /**
22      * The DataObject that owns this decorator.
23      * @var DataObject
24      */
25     protected $owner;
26     
27     /**
28      * The base class that this extension was applied to; $this->owner must be one of these
29      * @var DataObject
30      */
31     protected $ownerBaseClass;
32     
33     /**
34      * Reference counter to ensure that the owner isn't cleared until clearOwner() has
35      * been called as many times as setOwner()
36      */
37     private $ownerRefs = 0;
38     
39     public $class;
40     
41     function __construct() {
42         $this->class = get_class($this);
43     }
44 
45     /**
46      * Set the owner of this decorator.
47      * @param Object $owner The owner object,
48      * @param string $ownerBaseClass The base class that the extension is applied to; this may be
49      * the class of owner, or it may be a parent.  For example, if Versioned was applied to SiteTree,
50      * and then a Page object was instantiated, $owner would be a Page object, but $ownerBaseClass
51      * would be 'SiteTree'.
52      */
53     function setOwner($owner, $ownerBaseClass = null) {
54         if($owner) $this->ownerRefs++;
55         $this->owner = $owner;
56 
57         if($ownerBaseClass) $this->ownerBaseClass = $ownerBaseClass;
58         else if(!$this->ownerBaseClass && $owner) $this->ownerBaseClass = $owner->class;
59     }
60     
61     function clearOwner() {
62         if($this->ownerRefs <= 0) user_error("clearOwner() called more than setOwner()", E_USER_WARNING);
63         $this->ownerRefs--;
64         if($this->ownerRefs == 0) $this->owner = null;
65     }
66     
67     /**
68      * Returns the owner of this decorator
69      *
70      * @return Object
71      */
72     public function getOwner() {
73         return $this->owner;
74     }
75     
76     /**
77      * Helper method to strip eval'ed arguments from a string
78      * thats passed to {@link DataObject::$extensions} or 
79      * {@link Object::add_extension()}.
80      * 
81      * @param string $extensionStr E.g. "Versioned('Stage','Live')"
82      * @return string Extension classname, e.g. "Versioned"
83      */
84     public static function get_classname_without_arguments($extensionStr) {
85         return (($p = strpos($extensionStr, '(')) !== false) ? substr($extensionStr, 0, $p) : $extensionStr;
86     }
87     
88 }
89 
90 ?>