Drupal - Generically detecting changed fields in a custom form prior to saving a node

This, at long last, should work as a generic solution. Thanks to Clive and morbiD for all the input.

Pass both versions of the node to the following function. It will:

  1. Pull all of the detected content type's editable fields and their editable columns (i.e. items that could possibly appear on the custom form) from the database in a single query.

  2. Ignore fields and columns that are completely empty in both versions.

  3. Treat a field that has a different number of values between the two versions as a change.

  4. Iterate through every field, value, and column and compare the two versions.

  5. Compare items non-identically (!=) if they are numeric and identically (!==) if they are anything else.

  6. Immediately return TRUE on the first change it detects (since one change is enough to know we need to resave the node).

  7. Return FALSE if no change is detected after all the values are compared.

  8. Recursively compare field collections by loading them and their schema and passing the results to itself. This SHOULD even allow it to compare nested field collections. The code should NOT have any dependency on the Field Collection module.

Let me know if there are any more bugs or typos in this code.

/*
 * Pass both versions of the node to this function. Returns TRUE if it detects any changes and FALSE if not.
 * Pass field collections as an array keyed by field collection ID.
 *
 * @param object $old_entity
 *   The original (stored in the database) node object.
 *   This function may also pass itself a FieldCollectionItemEntity object to compare field collections.
 * @param object $new_entity
 *   The prepared node object for comparison.
 *   This function may also pass itself a FieldCollectionItemEntity object to compare field collections.
 */
function _fields_changed($old_entity, $new_entity) {
  // Check for node or field collection.
  $entity_is_field_collection = (get_class($old_entity) == 'FieldCollectionItemEntity');

  $bundle = ($entity_is_field_collection ? $old_entity->field_name : $old_entity->type);

  // Sanity check. Exit and throw an error if the content types don't match.
  if($bundle !== ($entity_is_field_collection ? $new_entity->field_name : $new_entity->type)) {
    drupal_set_message('Content type mismatch. Unable to save changes.', 'error');
    return FALSE;
  }

  // Get field info.
  $field_read_params = array(
    'entity_type' => ($entity_is_field_collection ? 'field_collection_item' : 'node'),
    'bundle' => $bundle
  );
  $fields_info = field_read_fields($field_read_params);

  foreach($fields_info as $field_name => $field_info) {
    $old_field = $old_entity->$field_name;
    $new_field = $new_entity->$field_name;

    // Check the number of values for each field, or if they are populated at all.
    $old_field_count = (isset($old_field[LANGUAGE_NONE]) ? count($old_field[LANGUAGE_NONE]) : 0);
    $new_field_count = (isset($new_field[LANGUAGE_NONE]) ? count($new_field[LANGUAGE_NONE]) : 0);

    if ($old_field_count != $new_field_count) {
      // The two versions have a different number of values. Something has changed.
      return TRUE;
    } elseif ($old_field_count > 0 && $new_field_count > 0) {
      // Both versions have an equal number of values. Time to compare.

      // See if this field is a field collection.
      if ($field_info['type'] == 'field_collection') {

        foreach ($new_field[LANGUAGE_NONE] as $delta => $values) {
          $old_field_collection = entity_load_unchanged('field_collection_item', $values['entity']->item_id);
          $new_field_collection = $values['entity'];

          if (_fields_changed($old_field_collection, $new_field_collection)) {
            return TRUE;
          }
        }
        unset($delta, $values);

      } else {
        foreach($old_field[LANGUAGE_NONE] as $delta => $value) {
          foreach($field_info['columns'] as $field_column_name => $field_column_info) {
            $old_value = $old_field[LANGUAGE_NONE][$delta][$field_column_name];
            $new_value = $new_field[LANGUAGE_NONE][$delta][$field_column_name];
            $field_column_type = $field_column_info['type'];

            // As with the overall field, exit if one version has a value and the other doesn't.
            if (isset($old_value) != isset($new_value)) {
              return TRUE;
            } elseif (isset($old_value) && isset($new_value)) {
              // The column stores numeric data so compare values non-identically.
              if (in_array($field_column_type, array('int', 'float', 'numeric'))) {
                if ($new_value != $old_value) {
                  return TRUE;
                }
              }
              // The column stores non-numeric data so compare values identically,
              elseif ($new_value !== $old_value) {
                return TRUE;
              }
            } else {
              // Included for clarity. Both values are empty so there was obviously no change.
            }
          } 
          unset($field_column_name, $field_column_info);
        }
        unset($delta, $value);
      }
    } else {
      // Included for clarity. Both values are empty so there was obviously no change.
    }
  }
  unset($field_name, $field_info);
  // End of field comparison loop.

  // We didn't find any changes. Don't resave the node.
  return FALSE;
}

Sometimes you are interested in knowing which fields have changed. In order to know that, you can use this version of the function:

/*
 * Pass both versions of the node to this function. Returns an array of
 * fields that were changed or an empty array if none were changed.
 * Pass field collections as an array keyed by field collection ID.
 *
 * @param object $old_entity
 *   The original (stored in the database) node object.
 *   This function may also pass itself a FieldCollectionItemEntity object to compare field collections.
 * @param object $new_entity
 *   The prepared node object for comparison.
 *   This function may also pass itself a FieldCollectionItemEntity object to compare field collections.
 */
function _fields_changed($old_entity, $new_entity) {
  // Check for node or field collection.
  $entity_is_field_collection = (get_class($old_entity) == 'FieldCollectionItemEntity');

  $bundle = ($entity_is_field_collection ? $old_entity->field_name : $old_entity->type);

  // Sanity check. Exit and throw an error if the content types don't match.
  if ($bundle !== ($entity_is_field_collection ? $new_entity->field_name : $new_entity->type)) {
    drupal_set_message('Content type mismatch. Unable to save changes.', 'error');
    return FALSE;
  }

  // Get field info.
  $field_read_params = array(
    'entity_type' => ($entity_is_field_collection ? 'field_collection_item' : 'node'),
    'bundle' => $bundle
  );
  $fields_info = field_read_fields($field_read_params);

  $fields_changed = array();

  foreach ($fields_info as $field_name => $field_info) {
    $old_field = $old_entity->$field_name;
    $new_field = $new_entity->$field_name;

    // Check the number of values for each field, or if they are populated at all.
    $old_field_count = (isset($old_field[LANGUAGE_NONE]) ? count($old_field[LANGUAGE_NONE]) : 0);
    $new_field_count = (isset($new_field[LANGUAGE_NONE]) ? count($new_field[LANGUAGE_NONE]) : 0);

    if ($old_field_count != $new_field_count) {
      // The two versions have a different number of values. Something has changed.
      $fields_changed[] = $field_name;
    }
    elseif ($old_field_count > 0 && $new_field_count > 0) {
      // Both versions have an equal number of values. Time to compare.

      // See if this field is a field collection.
      if ($field_info['type'] == 'field_collection') {

        foreach ($new_field[LANGUAGE_NONE] as $delta => $values) {
          $old_field_collection = entity_load_unchanged('field_collection_item', $values['entity']->item_id);
          $new_field_collection = $values['entity'];

          $fields_changed = array_merge($fields_changed, _fields_changed($old_field_collection, $new_field_collection));
        }
        unset($delta, $values);

      }
      else {
        foreach ($old_field[LANGUAGE_NONE] as $delta => $value) {
          foreach ($field_info['columns'] as $field_column_name => $field_column_info) {
            $old_value = $old_field[LANGUAGE_NONE][$delta][$field_column_name];
            $new_value = $new_field[LANGUAGE_NONE][$delta][$field_column_name];
            $field_column_type = $field_column_info['type'];

            // As with the overall field, exit if one version has a value and the other doesn't.
            if (isset($old_value) != isset($new_value)) {
              $fields_changed[] = $old_field;
            }
            elseif (isset($old_value) && isset($new_value)) {
              // The column stores numeric data so compare values non-identically.
              if (in_array($field_column_type, array(
                'int',
                'float',
                'numeric'
              ))) {
                if ($new_value != $old_value) {
                  $fields_changed[] = $field_name;
                }
              }
              // The column stores non-numeric data so compare values identically,
              elseif ($new_value !== $old_value) {
                $fields_changed[] = $field_name;
              }
            }
            else {
              // Included for clarity. Both values are empty so there was obviously no change.
            }
          }
          unset($field_column_name, $field_column_info);
        }
        unset($delta, $value);
      }
    }
    else {
      // Included for clarity. Both values are empty so there was obviously no change.
    }
  }
  unset($field_name, $field_info);
  // End of field comparison loop.

  return $fields_changed;
}

Sometimes you may want to make it so that changing certain fields of a node do not cause that node's "changed" timestamp to be updated. This could be implemented like as follows:

/**
 * Implements hook_node_presave().
 */
function mymodule_node_presave($node) {
  $fields_changed = _fields_changed($node->original, $node);
  $no_update_timestamp_fields = array('field_subject', 'field_keywords');
  if (!empty($fields_changed) &&
    empty(array_diff($fields_changed, $no_update_timestamp_fields))) {
    // Don't change the $node->changed timestamp if one of the fields has
    // been changed that should not affect the timestamp.
    $node->changed = $node->original->changed;
  }
}

EDIT (7/30/2013) Tightened up field collection support. Added support for fields with multiple values.

EDIT (7/31/2015) Added version of function which returns which fields have changed, and example use case.


Here's another, simpler, approach that avoids the complex server side value comparisons, and would work with any form:

  1. Use jQuery to detect if the form values have changed
  2. Set a hidden element value to indicate the form has changed.
  3. Check the hidden element value server side and process as required.

You could use a jQuery dirty form plugin such as https://github.com/codedance/jquery.AreYouSure

Although others that let you listen to the form changed / dirty status would also work.

Add a listener to set the value of a hidden form element:

Set the hidden form element to a default value of 'changed' to save by default for those users with javascript disabled (~2%).

e.g:

// Clear initial state for js-enabled user
$('input#hidden-indicator').val('')
// Add changed listener
$('#my-form').areYouSure({
    change: function() {
      // Set hidden element value
      if ($(this).hasClass('dirty')) {
        $('input#hidden-indicator').val('changed');
      } else {
        $('input#hidden-indicator').val('');
      }
    }
 });

You can then check the value of the hidden element

if ($form_state['values']['hidden_indicator'] == 'changed') { /* node_save($node) */ }

in your form validate / submit handlers.

Tags:

Entities

7

Related

Drupal - How do I write an additional field formatter for an existing field Drupal - Proper way to get the base path when including an image from a module? Drupal - How to get the node ID in jQuery/JavaScript Drupal - Why does the favicon sometimes not show up and generate "page not found" errors, and other times does show up Drupal - How can I move taxonomy terms to a different vocabulary and update term reference fields? Drupal - Does Google crawl Drupal sites in maintenance mode? Drupal - How do you delete a content type's URL aliases in bulk? Drupal - Adding title attribute to #type password_confirm Drupal - How to iterate over all the nodes from a content type Drupal - How can I set the value of a taxonomy term reference to multiple terms using PHP? Drupal - How do I POST a new node? Drupal - How do I use Font Awesome on a form submission button?

Recent Posts