Cascade delete referencing nodes
One of the most frequently requested feature about drupal nodereference is "on delete cascade" of referred nodes when you remove the referenced one. This is a pretty easy task to accomplish if you are using the
nodereferrer module:
function mymodule_nodeapi(&$node, $op, $params = NULL, $page = NULL) {
switch ($op) {
case 'delete':
if ($node->type == 'my_content_type_name') {
$referrers = array_keys(nodereferrer_referrers($node->nid));
foreach ($referrers as $referrer) {
node_delete($referrer);
}
}
break;
}
}
you can obtain the same effect without nodereferrer module: you have to query the database to obtain the referencing nodes nids like this:
function mymodule_nodeapi(&$node, $op, $params = NULL, $page = NULL) {
switch ($op) {
case 'delete':
if ($node->type == 'my_referenced_content_type_name') {
$result = db_query("SELECT nid FROM {content_type_referrer_name} r WHERE
r.field_content_reference_nid = %d", $node->nid);
while ($referrer = db_fetch_object($result)) {
node_delete($referrer->nid);
}
}
break;
}
}
Ok i guess you already knew those ones :]
Notifications when adding referencing nodes (ie. reviews)
Now the pulp: another task I had to implement for a website was "notify users about new nodes added referencing a content type". In other words: notify users when a review is written about an article. "Review" is a content type referencing another content type "article". I use the
notifications module and afaik there's nothing implemented there that take care of this issue.
I added this snippet in my custom module:
function _oninsert_notification(&$review, $op) {
if(module_exists('notifications')) {
$article = node_load($review->field_article_ref[0]['nid']);
$event = array(
'module' => 'node',
'uid' => $article->uid,
'oid' => $article->nid,
'type' => 'node',
'action' => $op,
'node' => $article,
'params' => array('nid' => $article->nid),
);
notifications_event($event);
}
}
and hooked this one into the nodeapi (review) insert operation.
This adds an event in the queue and will send an email to users that have subscribed an article once a review is written about it.
Tagging with referencing nodes
Last but not least: tagging. What if you have to tag an article
writing a review ? You have to add the tags to the referenced node (the article) but they normally are assigned to the review only. To get this behaviour I added this code to my module:
function mymodule_nodeapi(&$node, $op, $params = NULL, $page = NULL) {
switch ($op) {
case 'insert':
if (isset($node->field_article_ref[0]['nid'])) {
$article = node_load($node->field_article_ref[0]['nid']);
$tags = array_keys(taxonomy_node_get_terms($node));
foreach ($tags as $tag_tid) {
db_query('INSERT IGNORE INTO {term_node} (nid, vid, tid) VALUES (%d, %d, %d)',
$article->nid, $article->vid, $tag_tid);
}
break;
}
}
This works if you have a tag vocabulary assigned to both content types (this will save at least some joins :)
So now you have got tags assigned to both reviews and articles. Does it worth ? Sure !
You can now count how many times an article is tagged with a specified tag and create suggested tags and tag clouds:
/*
* nid is the article node nid
*/
function _most_used_tags($nid = NULL) {
$terms = array();
if (is_numeric($nid)) {
$referrers = array_keys(nodereferrer_referrers($nid));
if ($referrers) {
$result = db_query_range("SELECT t.*, COUNT(t.name) AS rweight FROM {term_data} t
INNER JOIN {term_node} n ON t.tid = n.tid WHERE t.vid = %d
AND n.vid IN (". db_placeholders($referrers) .")
GROUP BY t.tid ORDER BY rweight DESC",
array_merge(array(VID_TAGS) /* vocabulary vid */, $referrers),
0 /* starting offset */, 10 /* number of tags returned */);
while ($term = db_fetch_object($result)) {
$terms[$term->tid] = $term;
}
}
}
return $terms;
}
this will return the most used tags about the article. Those tags are added when inserting reviews.
Can the
community tags module do this ? Absolutely it can't. It does not let you associate tags inline with content editing/writing. This is the reason i didn't use it in my project.
my 3¢
