function nodeapi_example_nodeapi in Examples for Developers 6

Implementation of hook_nodeapi().

We will implement several node API operations here. This hook allows us to act on all major node operations, so we can manage our additional data appropriately.

Related topics

File

nodeapi_example/nodeapi_example.module, line 77

This is an example outlining how a module can be used to extend existing content types.

Code

function nodeapi_example_nodeapi(&$node, $op, $teaser, $page) {
  switch ($op) {

    // When the content editing form is submitted, we need to validate the input
    // to make sure the user made a selection, since we are requiring the rating
    // field. We have to check that the value has been set to avoid showing an
    // error message when a new blank form is presented. Calling form_set_error()
    // when the field is set but zero ensures not only that an error message is
    // presented, but also that the user must correct the error before being able
    // to submit the node.
    case 'validate':
      if (variable_get('nodeapi_example_' . $node->type, TRUE)) {
        if (isset($node->nodeapi_example_rating) && !$node->nodeapi_example_rating) {
          form_set_error('nodeapi_example_rating', t('You must rate this content.'));
        }
      }
      break;

    // Now we need to take care of loading one of the extended nodes from the
    // database. An array containing our extra field needs to be returned.
    case 'load':

      // we match against vid in order to keep up with the current revision
      $rating = db_result(db_query('SELECT rating FROM {nodeapi_example} WHERE vid = %d', $node->vid));
      return array(
        'nodeapi_example_rating' => $rating,
      );
      break;

    // Insert is called after the node has been validated and saved to the
    // database. It gives us a chance to create our own record in the database.
    case 'insert':
      if (variable_get('nodeapi_example_' . $node->type, 0)) {
        db_query('INSERT INTO {nodeapi_example} (nid, vid, rating) VALUES (%d, %d, %d)', $node->nid, $node->vid, $node->nodeapi_example_rating);
      }
      break;

    // Update is called when an existing node has been changed. Here, we use a
    // DELETE then an INSERT rather than an UPDATE. The reason is that a node
    // created before this module was installed won't already have a rating
    // saved so there would be nothing to update.
    case 'update':
      if (variable_get('nodeapi_example_' . $node->type, 0)) {
        db_query('DELETE FROM {nodeapi_example} WHERE vid = %d', $node->vid);
        db_query('INSERT INTO {nodeapi_example} (nid, vid, rating) VALUES (%d, %d, %d)', $node->nid, $node->vid, $node->nodeapi_example_rating);
      }
      break;

    // Delete is called when the node is being deleted, it gives us a chance
    // to delete the rating too.
    // This will delete all revisions as well.
    case 'delete':
      db_query('DELETE FROM {nodeapi_example} WHERE nid = %d', $node->nid);
      break;

    // When a node revision is deleted, we need to remove the corresponding
    // record from our table. The only way to handle revision deletion is by
    // implementing hook_nodeapi().
    case 'delete revision':

      // Notice that we're matching a single revision based on the node's vid.
      db_query('DELETE FROM {nodeapi_example} WHERE vid = %d', $node->vid);
      break;

    // Finally, we need to take care of displaying our rating when the node is
    // viewed. This operation is called after the node has already been prepared
    // into HTML and filtered as necessary, so we know we are dealing with an
    // HTML teaser and body. We will inject our additional information at the front
    // of the node copy.
    //
    // Using nodeapi('view') is more appropriate than using a filter here, because
    // filters transform user-supplied content, whereas we are extending it with
    // additional information.
    case 'view':
      if (variable_get('nodeapi_example_' . $node->type, 0)) {
        $node->content['nodeapi_example'] = array(
          '#value' => theme('nodeapi_example_rating', $node->nodeapi_example_rating),
          '#weight' => -1,
        );
      }
      break;
  }
}