Data Item Functions

This page discussed the actual (sept 2006, moodle 1.7) functions used to create, modify or delete data items.
Calculated parameters i.e {x1} are generated using the dataset parameters ( min, max, distribution) or edited directly by the teacher in the 3rd step of calculated questions creation or modifications. The code for doing this,is mostly in question/type/datasetdependent/datasetitems.php and in question/type/questiontype/generate_dataset_item($options) question/type/questiontype/comment_on_datasetitems($question, $data, $number) and backup and restore functions

In question/type/datasetdependent/datasetitems.php

// Handle adding of dataset items A data item have been either generated or reused and is presented in the form so it can be edited. When the add button is clicked

   // This twisted condition should effectively stop resubmits caused by reloads
   if (isset($form->addbutton) && $maxnumber + 1 == $form->numbertoadd) {
       $addeditem->number = $form->numbertoadd;
       foreach ($form->definition as $key => $defid) {
           $addeditem->definition = $datasetdefs[$defid]->id;
           $addeditem->value = $form->value[$key];
           if ($form->itemid[$key]) {
               // Reuse an previously used record
               $addeditem->id = $form->itemid[$key];
               if (!update_record('question_dataset_items', $addeditem)) {
                   error("Error: Unable to update dataset item");
               }
           } else {
               unset($addeditem->id);
               if (!insert_record('question_dataset_items', $addeditem)) {
                   error("Error: Unable to insert dataset item");
               }
           }

           foreach ($datasetdefs as $key => $newdef) {
               if (isset($newdef->id) && $newdef->itemcount <= $maxnumber) {
                   $newdef->itemcount = $maxnumber+1;
                   // Save the new value for options
                   update_record('question_dataset_definitions', $newdef);
               }
           }
       }
       // else Success:
       $maxnumber = $addeditem->number;

// removing of dataset items

When the remove button is clicked

   } else if (isset($form->deletebutton)
              && $maxnumber == $form->numbertodelete)  {
       // Simply decrease itemcount where == $maxnumber
       foreach ($datasetdefs as $datasetdef) {
           if ($datasetdef->itemcount == $maxnumber) {
               $datasetdef->itemcount--;
               if (!update_record('question_dataset_definitions',
                                  $datasetdef)) {
                    error("Error: Unable to update itemcount");
               }
           }
       }
       --$maxnumber;
   }
   make_upload_directory("$course->id");  // Just in case
   $grosscoursefiles = get_directory_list("$CFG->dataroot/$course->id",
                                      "$CFG->moddata");

The next form is prepared with a new or the last removed item is presented

// Generate a new dataset item (or reuse an old one)

   foreach ($datasetdefs as $defid => $datasetdef) {
       if (isset($datasetdef->id)) {
           $datasetdefs[$defid]->items = get_records_sql( // Use number as key!!
                   " SELECT number, definition, id, value
                     FROM {$CFG->prefix}question_dataset_items
                     WHERE definition = $datasetdef->id ");
       }

       if (isset($datasetdefs[$defid]->items[$maxnumber + 1]) && (
           empty($form->forceregeneration) &&
           isset($form->regenerateddefid) &&
           $form->regenerateddefid != $defid ||
           isset($form->deletebutton))) {
           // Reuse existing datasets
       } else {
           $datasetitem = new stdClass;
           $datasetitem->id =
            isset($datasetdefs[$defid]->items[$maxnumber + 1]->id)
            ? $datasetdefs[$defid]->items[$maxnumber + 1]->id : ;
           $datasetitem->number = $maxnumber + 1;
           if ($this->supports_dataset_item_generation()) {
               if (!empty($form->addbutton) || // If we added an item
                   !isset($form->value) ||     // If we don't have a value
                   $form->regenerateddefid == $defid) { // If we explicitly ask for regeneration
                       $datasetitem->value =
                        $this->generate_dataset_item($datasetdef->options);
               } else {
                   $definition = array_flip($form->definition);
                   $datasetitem->value = $form->value[$definition[$defid]];
               }
           } else {
               $datasetitem->value = ;
           }
           $datasetdefs[$defid]->items[$maxnumber + 1] = clone($datasetitem);
       }
   }

When you remove a data item, you don't delete it , you just decrease a counter in the dataset.

By doing it this way, this removed data item can be reused if you want it. (to be continued 1 sept 06)