question/type/questionbase.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  * This file defines the class {@link question_definition} and its subclasses.
  19  *
  20  * The type hierarchy is quite complex. Here is a summary:
  21  * - question_definition
  22  *   - question_information_item
  23  *   - question_with_responses implements question_manually_gradable
  24  *     - question_graded_automatically implements question_automatically_gradable
  25  *       - question_graded_automatically_with_countback implements question_automatically_gradable_with_countback
  26  *       - question_graded_by_strategy
  27  *
  28  * Other classes:
  29  * - question_classified_response
  30  * - question_answer
  31  * - question_hint
  32  *   - question_hint_with_parts
  33  * - question_first_matching_answer_grading_strategy implements question_grading_strategy
  34  *
  35  * Other interfaces:
  36  * - question_response_answer_comparer
  37  *
  38  * @package    moodlecore
  39  * @subpackage questiontypes
  40  * @copyright  2009 The Open University
  41  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  42  */
  43
  44
  45 defined('MOODLE_INTERNAL') || die();
  46
  47
  48 /**
  49  * The definition of a question of a particular type.
  50  *
  51  * This class is a close match to the question table in the database.
  52  * Definitions of question of a particular type normally subclass one of the
  53  * more specific classes {@link question_with_responses},
  54  * {@link question_graded_automatically} or {@link question_information_item}.
  55  *
  56  * @copyright  2009 The Open University
  57  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  58  */
  59 abstract class question_definition {
  60     /** @var integer id of the question in the datase, or null if this question
  61      * is not in the database. */
  62     public $id;
  63
  64     /** @var integer question category id. */
  65     public $category;
  66
  67     /** @var integer question context id. */
  68     public $contextid;
  69
  70     /** @var integer parent question id. */
  71     public $parent = 0;
  72
  73     /** @var question_type the question type this question is. */
  74     public $qtype;
  75
  76     /** @var string question name. */
  77     public $name;
  78
  79     /** @var string question text. */
  80     public $questiontext;
  81
  82     /** @var integer question test format. */
  83     public $questiontextformat;
  84
  85     /** @var string question general feedback. */
  86     public $generalfeedback;
  87
  88     /** @var integer question test format. */
  89     public $generalfeedbackformat;
  90
  91     /** @var number what this quetsion is marked out of, by default. */
  92     public $defaultmark = 1;
  93
  94     /** @var integer How many question numbers this question consumes. */
  95     public $length = 1;
  96
  97     /** @var number penalty factor of this question. */
  98     public $penalty = 0;
  99
 100     /** @var string unique identifier of this question. */
 101     public $stamp;
 102
 103     /** @var string unique identifier of this version of this question. */
 104     public $version;
 105
 106     /** @var boolean whethre this question has been deleted/hidden in the question bank. */
 107     public $hidden = 0;
 108
 109     /** @var integer timestamp when this question was created. */
 110     public $timecreated;
 111
 112     /** @var integer timestamp when this question was modified. */
 113     public $timemodified;
 114
 115     /** @var integer userid of the use who created this question. */
 116     public $createdby;
 117
 118     /** @var integer userid of the use who modified this question. */
 119     public $modifiedby;
 120
 121     /** @var array of question_hints. */
 122     public $hints = array();
 123
 124     /**
 125      * Constructor. Normally to get a question, you call
 126      * {@link question_bank::load_question()}, but questions can be created
 127      * directly, for example in unit test code.
 128      * @return unknown_type
 129      */
 130     public function __construct() {
 131     }
 132
 133     /**
 134      * @return the name of the question type (for example multichoice) that this
 135      * question is.
 136      */
 137     public function get_type_name() {
 138         return $this->qtype->name();
 139     }
 140
 141     /**
 142      * Creat the appropriate behaviour for an attempt at this quetsion,
 143      * given the desired (archetypal) behaviour.
 144      *
 145      * This default implementation will suit most normal graded questions.
 146      *
 147      * If your question is of a patricular type, then it may need to do something
 148      * different. For example, if your question can only be graded manually, then
 149      * it should probably return a manualgraded behaviour, irrespective of
 150      * what is asked for.
 151      *
 152      * If your question wants to do somthing especially complicated is some situations,
 153      * then you may wish to return a particular behaviour related to the
 154      * one asked for. For example, you migth want to return a
 155      * qbehaviour_interactive_adapted_for_myqtype.
 156      *
 157      * @param question_attempt $qa the attempt we are creating an behaviour for.
 158      * @param string $preferredbehaviour the requested type of behaviour.
 159      * @return question_behaviour the new behaviour object.
 160      */
 161     public function make_behaviour(question_attempt $qa, $preferredbehaviour) {
 162         return question_engine::make_archetypal_behaviour($preferredbehaviour, $qa);
 163     }
 164
 165     /**
 166      * Start a new attempt at this question, storing any information that will
 167      * be needed later in the step.
 168      *
 169      * This is where the question can do any initialisation required on a
 170      * per-attempt basis. For example, this is where the multiple choice
 171      * question type randomly shuffles the choices (if that option is set).
 172      *
 173      * Any information about how the question has been set up for this attempt
 174      * should be stored in the $step, by calling $step->set_qt_var(...).
 175      *
 176      * @param question_attempt_step The first step of the {@link question_attempt}
 177      *      being started. Can be used to store state.
 178      * @param int $varant which variant of this question to start. Will be between
 179      *      1 and {@link get_num_variants()} inclusive.
 180      */
 181     public function start_attempt(question_attempt_step $step, $variant) {
 182     }
 183
 184     /**
 185      * When an in-progress {@link question_attempt} is re-loaded from the
 186      * database, this method is called so that the question can re-initialise
 187      * its internal state as needed by this attempt.
 188      *
 189      * For example, the multiple choice question type needs to set the order
 190      * of the choices to the order that was set up when start_attempt was called
 191      * originally. All the information required to do this should be in the
 192      * $step object, which is the first step of the question_attempt being loaded.
 193      *
 194      * @param question_attempt_step The first step of the {@link question_attempt}
 195      *      being loaded.
 196      */
 197     public function apply_attempt_state(question_attempt_step $step) {
 198     }
 199
 200     /**
 201      * Generate a brief, plain-text, summary of this question. This is used by
 202      * various reports. This should show the particular variant of the question
 203      * as presented to students. For example, the calculated quetsion type would
 204      * fill in the particular numbers that were presented to the student.
 205      * This method will return null if such a summary is not possible, or
 206      * inappropriate.
 207      * @return string|null a plain text summary of this question.
 208      */
 209     public function get_question_summary() {
 210         return $this->html_to_text($this->questiontext, $this->questiontextformat);
 211     }
 212
 213     /**
 214      * @return int the number of vaiants that this question has.
 215      */
 216     public function get_num_variants() {
 217         return 1;
 218     }
 219
 220     /**
 221      * @return string that can be used to seed the pseudo-random selection of a
 222      *      variant.
 223      */
 224     public function get_variants_selection_seed() {
 225         return $this->stamp;
 226     }
 227
 228     /**
 229      * Some questions can return a negative mark if the student gets it wrong.
 230      *
 231      * This method returns the lowest mark the question can return, on the
 232      * fraction scale. that is, where the maximum possible mark is 1.0.
 233      *
 234      * @return number minimum fraction this question will ever return.
 235      */
 236     public function get_min_fraction() {
 237         return 0;
 238     }
 239
 240     /**
 241      * Given a response, rest the parts that are wrong.
 242      * @param array $response a response
 243      * @return array a cleaned up response with the wrong bits reset.
 244      */
 245     public function clear_wrong_from_response(array $response) {
 246         return array();
 247     }
 248
 249     /**
 250      * Return the number of subparts of this response that are right.
 251      * @param array $response a response
 252      * @return array with two elements, the number of correct subparts, and
 253      * the total number of subparts.
 254      */
 255     public function get_num_parts_right(array $response) {
 256         return array(null, null);
 257     }
 258
 259     /**
 260      * @param moodle_page the page we are outputting to.
 261      * @return qtype_renderer the renderer to use for outputting this question.
 262      */
 263     public function get_renderer(moodle_page $page) {
 264         return $page->get_renderer($this->qtype->plugin_name());
 265     }
 266
 267     /**
 268      * What data may be included in the form submission when a student submits
 269      * this question in its current state?
 270      *
 271      * This information is used in calls to optional_param. The parameter name
 272      * has {@link question_attempt::get_field_prefix()} automatically prepended.
 273      *
 274      * @return array|string variable name => PARAM_... constant, or, as a special case
 275      *      that should only be used in unavoidable, the constant question_attempt::USE_RAW_DATA
 276      *      meaning take all the raw submitted data belonging to this question.
 277      */
 278     public abstract function get_expected_data();
 279
 280     /**
 281      * What data would need to be submitted to get this question correct.
 282      * If there is more than one correct answer, this method should just
 283      * return one possibility. If it is not possible to compute a correct
 284      * response, this method should return null.
 285      *
 286      * @return array|null parameter name => value.
 287      */
 288     public abstract function get_correct_response();
 289
 290
 291     /**
 292      * Passed an array of data representing a student response this function transforms the array to a response array as would be
 293      * returned from the html form for this question instance.
 294      *
 295      * In most cases the array will just be returned as is. Some question types will need to transform the keys of the array in
 296      * as the meaning of the keys in the html form is deliberately obfuscated so that someone looking at the html does not get an
 297      * advantage.
 298      *
 299      * @param array $simulatedresponse an array of data representing a student response
 300      * @return array a response array as would be returned from the html form (but without prefixes)
 301      */
 302     public function prepare_simulated_post_data($simulatedresponse) {
 303         return $simulatedresponse;
 304     }
 305
 306     /**
 307      * Apply {@link format_text()} to some content with appropriate settings for
 308      * this question.
 309      *
 310      * @param string $text some content that needs to be output.
 311      * @param int $format the FORMAT_... constant.
 312      * @param question_attempt $qa the question attempt.
 313      * @param string $component used for rewriting file area URLs.
 314      * @param string $filearea used for rewriting file area URLs.
 315      * @param bool $clean Whether the HTML needs to be cleaned. Generally,
 316      *      parts of the question do not need to be cleaned, and student input does.
 317      * @return string the text formatted for output by format_text.
 318      */
 319     public function format_text($text, $format, $qa, $component, $filearea, $itemid,
 320             $clean = false) {
 321         $formatoptions = new stdClass();
 322         $formatoptions->noclean = !$clean;
 323         $formatoptions->para = false;
 324         $text = $qa->rewrite_pluginfile_urls($text, $component, $filearea, $itemid);
 325         return format_text($text, $format, $formatoptions);
 326     }
 327
 328     /**
 329      * Convert some part of the question text to plain text. This might be used,
 330      * for example, by get_response_summary().
 331      * @param string $text The HTML to reduce to plain text.
 332      * @param int $format the FORMAT_... constant.
 333      * @return string the equivalent plain text.
 334      */
 335     public function html_to_text($text, $format) {
 336         return question_utils::to_plain_text($text, $format);
 337     }
 338
 339     /** @return the result of applying {@link format_text()} to the question text. */
 340     public function format_questiontext($qa) {
 341         return $this->format_text($this->questiontext, $this->questiontextformat,
 342                 $qa, 'question', 'questiontext', $this->id);
 343     }
 344
 345     /** @return the result of applying {@link format_text()} to the general feedback. */
 346     public function format_generalfeedback($qa) {
 347         return $this->format_text($this->generalfeedback, $this->generalfeedbackformat,
 348                 $qa, 'question', 'generalfeedback', $this->id);
 349     }
 350
 351     /**
 352      * Checks whether the users is allow to be served a particular file.
 353      * @param question_attempt $qa the question attempt being displayed.
 354      * @param question_display_options $options the options that control display of the question.
 355      * @param string $component the name of the component we are serving files for.
 356      * @param string $filearea the name of the file area.
 357      * @param array $args the remaining bits of the file path.
 358      * @param bool $forcedownload whether the user must be forced to download the file.
 359      * @return bool true if the user can access this file.
 360      */
 361     public function check_file_access($qa, $options, $component, $filearea, $args, $forcedownload) {
 362         if ($component == 'question' && $filearea == 'questiontext') {
 363             // Question text always visible.
 364             return true;
 365
 366         } else if ($component == 'question' && $filearea == 'generalfeedback') {
 367             return $options->generalfeedback;
 368
 369         } else {
 370             // Unrecognised component or filearea.
 371             return false;
 372         }
 373     }
 374 }
 375
 376
 377 /**
 378  * This class represents a 'question' that actually does not allow the student
 379  * to respond, like the description 'question' type.
 380  *
 381  * @copyright  2009 The Open University
 382  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 383  */
 384 class question_information_item extends question_definition {
 385     public function __construct() {
 386         parent::__construct();
 387         $this->defaultmark = 0;
 388         $this->penalty = 0;
 389         $this->length = 0;
 390     }
 391
 392     public function make_behaviour(question_attempt $qa, $preferredbehaviour) {
 393         question_engine::load_behaviour_class('informationitem');
 394         return new qbehaviour_informationitem($qa, $preferredbehaviour);
 395     }
 396
 397     public function get_expected_data() {
 398         return array();
 399     }
 400
 401     public function get_correct_response() {
 402         return array();
 403     }
 404
 405     public function get_question_summary() {
 406         return null;
 407     }
 408 }
 409
 410
 411 /**
 412  * Interface that a {@link question_definition} must implement to be usable by
 413  * the manual graded behaviour.
 414  *
 415  * @copyright  2009 The Open University
 416  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 417  */
 418 interface question_manually_gradable {
 419     /**
 420      * Used by many of the behaviours, to work out whether the student's
 421      * response to the question is complete. That is, whether the question attempt
 422      * should move to the COMPLETE or INCOMPLETE state.
 423      *
 424      * @param array $response responses, as returned by
 425      *      {@link question_attempt_step::get_qt_data()}.
 426      * @return bool whether this response is a complete answer to this question.
 427      */
 428     public function is_complete_response(array $response);
 429
 430     /**
 431      * Use by many of the behaviours to determine whether the student's
 432      * response has changed. This is normally used to determine that a new set
 433      * of responses can safely be discarded.
 434      *
 435      * @param array $prevresponse the responses previously recorded for this question,
 436      *      as returned by {@link question_attempt_step::get_qt_data()}
 437      * @param array $newresponse the new responses, in the same format.
 438      * @return bool whether the two sets of responses are the same - that is
 439      *      whether the new set of responses can safely be discarded.
 440      */
 441     public function is_same_response(array $prevresponse, array $newresponse);
 442
 443     /**
 444      * Produce a plain text summary of a response.
 445      * @param $response a response, as might be passed to {@link grade_response()}.
 446      * @return string a plain text summary of that response, that could be used in reports.
 447      */
 448     public function summarise_response(array $response);
 449
 450     /**
 451      * Categorise the student's response according to the categories defined by
 452      * get_possible_responses.
 453      * @param $response a response, as might be passed to {@link grade_response()}.
 454      * @return array subpartid => {@link question_classified_response} objects.
 455      *      returns an empty array if no analysis is possible.
 456      */
 457     public function classify_response(array $response);
 458 }
 459
 460
 461 /**
 462  * This class is used in the return value from
 463  * {@link question_manually_gradable::classify_response()}.
 464  *
 465  * @copyright  2010 The Open University
 466  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 467  */
 468 class question_classified_response {
 469     /**
 470      * @var string the classification of this response the student gave to this
 471      * part of the question. Must match one of the responseclasses returned by
 472      * {@link question_type::get_possible_responses()}.
 473      */
 474     public $responseclassid;
 475     /** @var string the actual response the student gave to this part. */
 476     public $response;
 477     /** @var number the fraction this part of the response earned. */
 478     public $fraction;
 479     /**
 480      * Constructor, just an easy way to set the fields.
 481      * @param string $responseclassid see the field descriptions above.
 482      * @param string $response see the field descriptions above.
 483      * @param number $fraction see the field descriptions above.
 484      */
 485     public function __construct($responseclassid, $response, $fraction) {
 486         $this->responseclassid = $responseclassid;
 487         $this->response = $response;
 488         $this->fraction = $fraction;
 489     }
 490
 491     public static function no_response() {
 492         return new question_classified_response(null, get_string('noresponse', 'question'), null);
 493     }
 494 }
 495
 496
 497 /**
 498  * Interface that a {@link question_definition} must implement to be usable by
 499  * the various automatic grading behaviours.
 500  *
 501  * @copyright  2009 The Open University
 502  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 503  */
 504 interface question_automatically_gradable extends question_manually_gradable {
 505     /**
 506      * Use by many of the behaviours to determine whether the student
 507      * has provided enough of an answer for the question to be graded automatically,
 508      * or whether it must be considered aborted.
 509      *
 510      * @param array $response responses, as returned by
 511      *      {@link question_attempt_step::get_qt_data()}.
 512      * @return bool whether this response can be graded.
 513      */
 514     public function is_gradable_response(array $response);
 515
 516     /**
 517      * In situations where is_gradable_response() returns false, this method
 518      * should generate a description of what the problem is.
 519      * @return string the message.
 520      */
 521     public function get_validation_error(array $response);
 522
 523     /**
 524      * Grade a response to the question, returning a fraction between
 525      * get_min_fraction() and 1.0, and the corresponding {@link question_state}
 526      * right, partial or wrong.
 527      * @param array $response responses, as returned by
 528      *      {@link question_attempt_step::get_qt_data()}.
 529      * @return array (number, integer) the fraction, and the state.
 530      */
 531     public function grade_response(array $response);
 532
 533     /**
 534      * Get one of the question hints. The question_attempt is passed in case
 535      * the question type wants to do something complex. For example, the
 536      * multiple choice with multiple responses question type will turn off most
 537      * of the hint options if the student has selected too many opitions.
 538      * @param int $hintnumber Which hint to display. Indexed starting from 0
 539      * @param question_attempt $qa The question_attempt.
 540      */
 541     public function get_hint($hintnumber, question_attempt $qa);
 542
 543     /**
 544      * Generate a brief, plain-text, summary of the correct answer to this question.
 545      * This is used by various reports, and can also be useful when testing.
 546      * This method will return null if such a summary is not possible, or
 547      * inappropriate.
 548      * @return string|null a plain text summary of the right answer to this question.
 549      */
 550     public function get_right_answer_summary();
 551 }
 552
 553
 554 /**
 555  * Interface that a {@link question_definition} must implement to be usable by
 556  * the interactivecountback behaviour.
 557  *
 558  * @copyright  2010 The Open University
 559  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 560  */
 561 interface question_automatically_gradable_with_countback extends question_automatically_gradable {
 562     /**
 563      * Work out a final grade for this attempt, taking into account all the
 564      * tries the student made.
 565      * @param array $responses the response for each try. Each element of this
 566      * array is a response array, as would be passed to {@link grade_response()}.
 567      * There may be between 1 and $totaltries responses.
 568      * @param int $totaltries The maximum number of tries allowed.
 569      * @return numeric the fraction that should be awarded for this
 570      * sequence of response.
 571      */
 572     public function compute_final_grade($responses, $totaltries);
 573 }
 574
 575
 576 /**
 577  * This class represents a real question. That is, one that is not a
 578  * {@link question_information_item}.
 579  *
 580  * @copyright  2009 The Open University
 581  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 582  */
 583 abstract class question_with_responses extends question_definition
 584         implements question_manually_gradable {
 585     public function classify_response(array $response) {
 586         return array();
 587     }
 588 }
 589
 590
 591 /**
 592  * This class represents a question that can be graded automatically.
 593  *
 594  * @copyright  2009 The Open University
 595  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 596  */
 597 abstract class question_graded_automatically extends question_with_responses
 598         implements question_automatically_gradable {
 599     /** @var Some question types have the option to show the number of sub-parts correct. */
 600     public $shownumcorrect = false;
 601
 602     public function is_gradable_response(array $response) {
 603         return $this->is_complete_response($response);
 604     }
 605
 606     public function get_right_answer_summary() {
 607         $correctresponse = $this->get_correct_response();
 608         if (empty($correctresponse)) {
 609             return null;
 610         }
 611         return $this->summarise_response($correctresponse);
 612     }
 613
 614     /**
 615      * Check a request for access to a file belonging to a combined feedback field.
 616      * @param question_attempt $qa the question attempt being displayed.
 617      * @param question_display_options $options the options that control display of the question.
 618      * @param string $filearea the name of the file area.
 619      * @return bool whether access to the file should be allowed.
 620      */
 621     protected function check_combined_feedback_file_access($qa, $options, $filearea) {
 622         $state = $qa->get_state();
 623
 624         if (!$state->is_finished()) {
 625             $response = $qa->get_last_qt_data();
 626             if (!$this->is_gradable_response($response)) {
 627                 return false;
 628             }
 629             list($notused, $state) = $this->grade_response($response);
 630         }
 631
 632         return $options->feedback && $state->get_feedback_class() . 'feedback' == $filearea;
 633     }
 634
 635     /**
 636      * Check a request for access to a file belonging to a hint.
 637      * @param question_attempt $qa the question attempt being displayed.
 638      * @param question_display_options $options the options that control display of the question.
 639      * @param array $args the remaining bits of the file path.
 640      * @return bool whether access to the file should be allowed.
 641      */
 642     protected function check_hint_file_access($qa, $options, $args) {
 643         if (!$options->feedback) {
 644             return false;
 645         }
 646         $hint = $qa->get_applicable_hint();
 647         $hintid = reset($args); // Itemid is hint id.
 648         return $hintid == $hint->id;
 649     }
 650
 651     public function get_hint($hintnumber, question_attempt $qa) {
 652         if (!isset($this->hints[$hintnumber])) {
 653             return null;
 654         }
 655         return $this->hints[$hintnumber];
 656     }
 657
 658     public function format_hint(question_hint $hint, question_attempt $qa) {
 659         return $this->format_text($hint->hint, $hint->hintformat, $qa,
 660                 'question', 'hint', $hint->id);
 661     }
 662 }
 663
 664
 665 /**
 666  * This class represents a question that can be graded automatically with
 667  * countback grading in interactive mode.
 668  *
 669  * @copyright  2010 The Open University
 670  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 671  */
 672 abstract class question_graded_automatically_with_countback
 673         extends question_graded_automatically
 674         implements question_automatically_gradable_with_countback {
 675
 676     public function make_behaviour(question_attempt $qa, $preferredbehaviour) {
 677         if ($preferredbehaviour == 'interactive') {
 678             return question_engine::make_behaviour('interactivecountback',
 679                     $qa, $preferredbehaviour);
 680         }
 681         return question_engine::make_archetypal_behaviour($preferredbehaviour, $qa);
 682     }
 683 }
 684
 685
 686 /**
 687  * This class represents a question that can be graded automatically by using
 688  * a {@link question_grading_strategy}.
 689  *
 690  * @copyright  2009 The Open University
 691  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 692  */
 693 abstract class question_graded_by_strategy extends question_graded_automatically {
 694     /** @var question_grading_strategy the strategy to use for grading. */
 695     protected $gradingstrategy;
 696
 697     /** @param question_grading_strategy  $strategy the strategy to use for grading. */
 698     public function __construct(question_grading_strategy $strategy) {
 699         parent::__construct();
 700         $this->gradingstrategy = $strategy;
 701     }
 702
 703     public function get_correct_response() {
 704         $answer = $this->get_correct_answer();
 705         if (!$answer) {
 706             return array();
 707         }
 708
 709         return array('answer' => $answer->answer);
 710     }
 711
 712     /**
 713      * Get an answer that contains the feedback and fraction that should be
 714      * awarded for this resonse.
 715      * @param array $response a response.
 716      * @return question_answer the matching answer.
 717      */
 718     public function get_matching_answer(array $response) {
 719         return $this->gradingstrategy->grade($response);
 720     }
 721
 722     /**
 723      * @return question_answer an answer that contains the a response that would
 724      *      get full marks.
 725      */
 726     public function get_correct_answer() {
 727         return $this->gradingstrategy->get_correct_answer();
 728     }
 729
 730     public function grade_response(array $response) {
 731         $answer = $this->get_matching_answer($response);
 732         if ($answer) {
 733             return array($answer->fraction,
 734                     question_state::graded_state_for_fraction($answer->fraction));
 735         } else {
 736             return array(0, question_state::$gradedwrong);
 737         }
 738     }
 739
 740     public function classify_response(array $response) {
 741         if (empty($response['answer'])) {
 742             return array($this->id => question_classified_response::no_response());
 743         }
 744
 745         $ans = $this->get_matching_answer($response);
 746         if (!$ans) {
 747             return array($this->id => new question_classified_response(
 748                     0, $response['answer'], 0));
 749         }
 750
 751         return array($this->id => new question_classified_response(
 752                 $ans->id, $response['answer'], $ans->fraction));
 753     }
 754 }
 755
 756
 757 /**
 758  * Class to represent a question answer, loaded from the question_answers table
 759  * in the database.
 760  *
 761  * @copyright  2009 The Open University
 762  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 763  */
 764 class question_answer {
 765     /** @var integer the answer id. */
 766     public $id;
 767
 768     /** @var string the answer. */
 769     public $answer;
 770
 771     /** @var integer one of the FORMAT_... constans. */
 772     public $answerformat = FORMAT_PLAIN;
 773
 774     /** @var number the fraction this answer is worth. */
 775     public $fraction;
 776
 777     /** @var string the feedback for this answer. */
 778     public $feedback;
 779
 780     /** @var integer one of the FORMAT_... constans. */
 781     public $feedbackformat;
 782
 783     /**
 784      * Constructor.
 785      * @param int $id the answer.
 786      * @param string $answer the answer.
 787      * @param number $fraction the fraction this answer is worth.
 788      * @param string $feedback the feedback for this answer.
 789      * @param int $feedbackformat the format of the feedback.
 790      */
 791     public function __construct($id, $answer, $fraction, $feedback, $feedbackformat) {
 792         $this->id = $id;
 793         $this->answer = $answer;
 794         $this->fraction = $fraction;
 795         $this->feedback = $feedback;
 796         $this->feedbackformat = $feedbackformat;
 797     }
 798 }
 799
 800
 801 /**
 802  * Class to represent a hint associated with a question.
 803  * Used by iteractive mode, etc. A question has an array of these.
 804  *
 805  * @copyright  2010 The Open University
 806  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 807  */
 808 class question_hint {
 809     /** @var integer The hint id. */
 810     public $id;
 811     /** @var string The feedback hint to be shown. */
 812     public $hint;
 813     /** @var integer The corresponding text FORMAT_... type. */
 814     public $hintformat;
 815
 816     /**
 817      * Constructor.
 818      * @param int the hint id from the database.
 819      * @param string $hint The hint text
 820      * @param int the corresponding text FORMAT_... type.
 821      */
 822     public function __construct($id, $hint, $hintformat) {
 823         $this->id = $id;
 824         $this->hint = $hint;
 825         $this->hintformat = $hintformat;
 826     }
 827
 828     /**
 829      * Create a basic hint from a row loaded from the question_hints table in the database.
 830      * @param object $row with $row->hint set.
 831      * @return question_hint
 832      */
 833     public static function load_from_record($row) {
 834         return new question_hint($row->id, $row->hint, $row->hintformat);
 835     }
 836
 837     /**
 838      * Adjust this display options according to the hint settings.
 839      * @param question_display_options $options
 840      */
 841     public function adjust_display_options(question_display_options $options) {
 842         // Do nothing.
 843     }
 844 }
 845
 846
 847 /**
 848  * An extension of {@link question_hint} for questions like match and multiple
 849  * choice with multile answers, where there are options for whether to show the
 850  * number of parts right at each stage, and to reset the wrong parts.
 851  *
 852  * @copyright  2010 The Open University
 853  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 854  */
 855 class question_hint_with_parts extends question_hint {
 856     /** @var boolean option to show the number of sub-parts of the question that were right. */
 857     public $shownumcorrect;
 858
 859     /** @var boolean option to clear the parts of the question that were wrong on retry. */
 860     public $clearwrong;
 861
 862     /**
 863      * Constructor.
 864      * @param int the hint id from the database.
 865      * @param string $hint The hint text
 866      * @param int the corresponding text FORMAT_... type.
 867      * @param bool $shownumcorrect whether the number of right parts should be shown
 868      * @param bool $clearwrong whether the wrong parts should be reset.
 869      */
 870     public function __construct($id, $hint, $hintformat, $shownumcorrect, $clearwrong) {
 871         parent::__construct($id, $hint, $hintformat);
 872         $this->shownumcorrect = $shownumcorrect;
 873         $this->clearwrong = $clearwrong;
 874     }
 875
 876     /**
 877      * Create a basic hint from a row loaded from the question_hints table in the database.
 878      * @param object $row with $row->hint, ->shownumcorrect and ->clearwrong set.
 879      * @return question_hint_with_parts
 880      */
 881     public static function load_from_record($row) {
 882         return new question_hint_with_parts($row->id, $row->hint, $row->hintformat,
 883                 $row->shownumcorrect, $row->clearwrong);
 884     }
 885
 886     public function adjust_display_options(question_display_options $options) {
 887         parent::adjust_display_options($options);
 888         if ($this->clearwrong) {
 889             $options->clearwrong = true;
 890         }
 891         $options->numpartscorrect = $this->shownumcorrect;
 892     }
 893 }
 894
 895
 896 /**
 897  * This question_grading_strategy interface. Used to share grading code between
 898  * questions that that subclass {@link question_graded_by_strategy}.
 899  *
 900  * @copyright  2009 The Open University
 901  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 902  */
 903 interface question_grading_strategy {
 904     /**
 905      * Return a question answer that describes the outcome (fraction and feeback)
 906      * for a particular respons.
 907      * @param array $response the response.
 908      * @return question_answer the answer describing the outcome.
 909      */
 910     public function grade(array $response);
 911
 912     /**
 913      * @return question_answer an answer that contains the a response that would
 914      *      get full marks.
 915      */
 916     public function get_correct_answer();
 917 }
 918
 919
 920 /**
 921  * This interface defines the methods that a {@link question_definition} must
 922  * implement if it is to be graded by the
 923  * {@link question_first_matching_answer_grading_strategy}.
 924  *
 925  * @copyright  2009 The Open University
 926  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 927  */
 928 interface question_response_answer_comparer {
 929     /** @return array of {@link question_answers}. */
 930     public function get_answers();
 931
 932     /**
 933      * @param array $response the response.
 934      * @param question_answer $answer an answer.
 935      * @return bool whether the response matches the answer.
 936      */
 937     public function compare_response_with_answer(array $response, question_answer $answer);
 938 }
 939
 940
 941 /**
 942  * This grading strategy is used by question types like shortanswer an numerical.
 943  * It gets a list of possible answers from the question, and returns the first one
 944  * that matches the given response. It returns the first answer with fraction 1.0
 945  * when asked for the correct answer.
 946  *
 947  * @copyright  2009 The Open University
 948  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 949  */
 950 class question_first_matching_answer_grading_strategy implements question_grading_strategy {
 951     /**
 952      * @var question_response_answer_comparer (presumably also a
 953      * {@link question_definition}) the question we are doing the grading for.
 954      */
 955     protected $question;
 956
 957     /**
 958      * @param question_response_answer_comparer $question (presumably also a
 959      * {@link question_definition}) the question we are doing the grading for.
 960      */
 961     public function __construct(question_response_answer_comparer $question) {
 962         $this->question = $question;
 963     }
 964
 965     public function grade(array $response) {
 966         foreach ($this->question->get_answers() as $aid => $answer) {
 967             if ($this->question->compare_response_with_answer($response, $answer)) {
 968                 $answer->id = $aid;
 969                 return $answer;
 970             }
 971         }
 972         return null;
 973     }
 974
 975     public function get_correct_answer() {
 976         foreach ($this->question->get_answers() as $answer) {
 977             $state = question_state::graded_state_for_fraction($answer->fraction);
 978             if ($state == question_state::$gradedright) {
 979                 return $answer;
 980             }
 981         }
 982         return null;
 983     }
 984 }