Drupal 7 Module Development

Chapter 9
Using the new hook_node_access_records_alter() and hook_node_grants_
alter(), we can fundamentally alter how any other node access module behaves.
To do so, we will create the Role Access Extend module to implement our
optional behaviors.
Using hook_node_grants_alter()
When using node access alter hooks, we must decide: Should we alter what is saved
in the database {node_access} or should we alter how the user interacts with the
stored data? Since we might want to turn this module off, the best solution is to leave
{node_access} alone and instead alter the grants on page load. We do this with the
new Drupal 7 hook_node_grants_alter().
hook_node_grants_alter() is a very powerful hook. After Drupal has gathered all
the node access permissions set by your site's modules, this hook fires and allows a
module to modify the cumulative $grants array by reference. In structure, the hook
looks much like hook_node_grants(). It passes &$grants, plus the requesting user's
$account object and the requested $op.
To make our first rule work, we need to control the View operation and decide
which user roles may view content as if they were in the authenticated user
role. First, we create our role_access_extend.info file, and then we create a
role_access_extend.module.