Drupal 7 Module Development

Node Access
Note that we do not have access to the $node object here. This is because the node
access API is used to provide advanced filtering of queries, both for single nodes and
for groups of nodes. This level of abstraction is what makes node access work.
So our Role Access module must determine what permissions our current user has.
This is a fairly simple operation, since user roles are attached to the $account object:
/**
* Implement hook_node_grants().
*/
function role_access_node_grants($account, $op) {
// Get the user roles.
$roles = array_keys($account->roles);
}
// Error checking.
if (empty($roles)) {
return array();
}
// Initialize a $grants array.
$grants = array();
// Iterate through the roles.
foreach ($roles as $grant_id) {
$grants['role_access'][] = $grant_id;
}
// Return the grants.
return $grants;
Again, we are expected to return a $grants array. This array is keyed by the realm(s)
of our module. Each realm may then declare an array of grant ids.
These values are then concatenated for all modules on the site, and a final $grants
array is constructed. This array is used to alter queries to the {node} table in order
to enforce our node access rules.
These grants must match those provided in hook_node_access_records(),
otherwise, the grants will fail and the operation will be denied.
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