Drupal 7 Module Development

Chapter 9
The key to Devel Node Access is its own internal hook system, which allows node
access modules to declare a readable summary of their rules. Writing this hook is
good practice, since it helps you articulate what your module does.
Using hook_node_access_explain()
hook_node_access_explain() is a function that should be responded to only by the
module that sets the grants returned by hook_node_access_records(). So for our
sample, we will implement it in the base Role Access module.
The hook passes one argument $row, which is an object representing one row from
the {node_access} table. Your module should inspect the data, and respond with
information if the $row belongs to it.
/**
* Implement hook_node_access_explain().
*/
function role_access_node_access_explain($row) {
// If not our grant, ignore.
if ($row->realm != 'role_access') {
return NULL;
}
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