How to prevent deleting a term if used?

Question

Is there any way to prevent deleting a taxonomy term if it used in any node ?

I have a Taxonomy that is used in Field Collection in my Content Type , I want to warn/prevent deletion of any Term in that Taxonomy if it is used in any node.

I checked taxonomy_term_confirm_delete it is where the confirmation message is formed, I read from some posts about using

db_query("SELECT COUNT(nid) FROM {taxonomy_index} WHERE tid = :aid", array(':aid' => $tid) )->fetchField()

to get the number of nodes a term is used in but this is not working in my case -maybe because the taxonomy is in field collection ?

Answer 1

I wrote an article tackling this problem.

In short, you have to use hook_form_alter on the form taxonomy_form_term and use the function taxonomy_select_nodes() to check if a node uses the term in question.

You can just go ahead and copy the code from the article into your custom module (naming the 'mymodule_form_alter' accordingly to your module's name), flush the caches and that should do it.

Answer 2

I think you can use taxonomy_select_nodes function to achieve this.

Return nodes attached to a term across all field instances.

taxonomy_select_nodes($tid, $pager = TRUE, $limit = FALSE, $order = array('t.sticky' => 'DESC', 't.created' => 'DESC'))

Parameters

$tid: The term ID.

$pager: Boolean to indicate whether a pager should be used.

$limit: Integer. The maximum number of nodes to find. Set to FALSE for no limit.

$order: An array of fields and directions.

Answer 3

For Drupal 8.

Prevent Term Delete module is built to prevent the taxonomy term deletion when the taxonomy term is associated with nodes or entities using taxonomy term reference.