library/Git/Lazy.php

   1 <?php
   2
   3 /**
   4  * Implements lazy loading of properties.
   5  *
   6  * In the Python implementation, this is implemented as a
   7  * mix-in. However, we don't have this capability in PHP, so
   8  * we implement is as a super-class (as multiple mix-ins
   9  * are not used). If this ends up being a problem, rewrite
  10  * this class to be a decorator, and create a factory for
  11  * Git objects.
  12  *
  13  * @warning Subclasses should be careful to call __get manually
  14  *          if they're not sure if a particular property will
  15  *          be initialized or not; because they have full access
  16  *          __get will not be called automatically.
  17  */
  18 abstract class Git_Lazy {
  19     /**
  20      * Whether or not this class's contents have been loaded.
  21      */
  22     private $_baked = false;
  23     /**
  24      * Marks the class as baked; use this if you loaded the
  25      * contents yourself.
  26      */
  27     protected function markBaked() {
  28         $this->_baked = true;
  29     }
  30     /**
  31      * Implements public lazy loading.
  32      */
  33     public function __get($name) {
  34         if ($name[0] == '_') throw new Git_Exception('Cannot access private property ' . $name);
  35         // Quick and easy way of emulating Python's @property decorator
  36         if (method_exists($this, $name)) {
  37             return $this->$name();
  38         }
  39         if (isset($this->$name)) return $this->$name;
  40         if (!$this->_baked) {
  41             $this->bake();
  42             $this->_baked = true;
  43         }
  44         return $this->$name;
  45     }
  46     /**
  47      * Implements the loading operation; after this method is
  48      * called the class should be ready to go.
  49      */
  50     abstract protected function bake();
  51 }