availability/classes/capability_checker.php

   1 <?php
   2 // This file is part of Moodle - http://moodle.org/
   3 //
   4 // Moodle is free software: you can redistribute it and/or modify
   5 // it under the terms of the GNU General Public License as published by
   6 // the Free Software Foundation, either version 3 of the License, or
   7 // (at your option) any later version.
   8 //
   9 // Moodle is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13 //
  14 // You should have received a copy of the GNU General Public License
  15 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
  16
  17 /**
  18  * Used while evaluating conditions in bulk.
  19  *
  20  * This object caches get_users_by_capability results in case they are needed
  21  * by multiple conditions.
  22  *
  23  * @package core_availability
  24  * @copyright 2014 The Open University
  25  * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  26  */
  27
  28 namespace core_availability;
  29
  30 defined('MOODLE_INTERNAL') || die();
  31
  32 /**
  33  * Used while evaluating conditions in bulk.
  34  *
  35  * This object caches get_users_by_capability results in case they are needed
  36  * by multiple conditions.
  37  *
  38  * @package core_availability
  39  * @copyright 2014 The Open University
  40  * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  41  */
  42 class capability_checker {
  43     /** @var \context Course or module context */
  44     protected $context;
  45
  46     /** @var array Associative array of capability => result */
  47     protected $cache = array();
  48
  49     /**
  50      * Constructs for given context.
  51      *
  52      * @param \context $context Context
  53      */
  54     public function __construct(\context $context) {
  55         $this->context = $context;
  56     }
  57
  58     /**
  59      * Gets users on course who have the specified capability. Returns an array
  60      * of user objects which only contain the 'id' field. If the same capability
  61      * has already been checked (e.g. by another condition) then a cached
  62      * result will be used.
  63      *
  64      * More fields are not necessary because this code is only used to filter
  65      * users from an existing list.
  66      *
  67      * @param string $capability Required capability
  68      * @return array Associative array of user id => objects containing only id
  69      */
  70     public function get_users_by_capability($capability) {
  71         if (!array_key_exists($capability, $this->cache)) {
  72             $this->cache[$capability] = get_users_by_capability(
  73                     $this->context, $capability, 'u.id');
  74         }
  75         return $this->cache[$capability];
  76     }
  77 }