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   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  }