Viewing of content type restriction

gistfile1.aw

<?php
/**
 * Implements hook_menu_alter().
 */
function module_menu_alter(&$items) {
  $old_callback = $items['node/%node']['access callback'];
  $old_args = $items['node/%node']['access arguments'];
  
  // Overrides the access callback to remove access to note content
  $items['node/%node']['access callback'] = '_note_node_view_access';
  $items['node/%node']['access arguments'] = array(
    $old_callback,
    $old_args
  );
}

/**
 * Restricts access to note content
 *
 * @param string $old_callback 
 * @param string $old_args 
 * @return boolean
 * @author Maarten Jacobs
 */
function _note_node_view_access($old_callback, $old_args) {
  $nid = arg($old_args[1]);
  $node = node_load($nid);
  $old_args[1] = $node;
  if ($node->type == 'note') {
    // Restrict access for notes
    return false;
  } else {
    return $old_callback($old_args[0], $old_args[1], $old_args[2]);
  }
}