How do I limit the allowed taxonomy terms basing on the content type?

Question

I have two different content types, Computer and Chemistry, and taxonomy terms for all articles (content types) which store the methodology of the article. The taxonomy hierarchy is the following.

• Articles
  • Computer
    • Arithmetic (Term ID: 1)
    • DMA (Term ID: 2) // abbreviation for "Direct Memory Access"
  • Chemistry
    • NGE (Term ID: 3) // abbreviation for "Noble Gas Elements"
    • DMA (Term ID: 4) // abbreviation for "Dynamic Mechanical Analysis"

When users are creating or editing a node of type Chemistry, just NGE and DMA (whose ID is 4) should be allowed to select.

I only need one taxonomy vocabulary, since there are too many content types, and if I want to add a vocabulary for each of them, then it leads too many vocabularies; more importantly it removes the ability of freely navigating in different types using taxonomy hierarchy.

How do I limit the allowed taxonomy terms basing on the content type?

Answer 1

According to my choice you should use hook_form_alter to bind taxonomy list based on article type.

function MY_MODULE_NAME_form_alter(&$form, &$form_state, $form_id) {
  if ($form_id == 'my_form_id') {
    $default_value = 0;
    $options = getArticles('Computer','Articles');
    $form['your_taxonomy_field_name'] = array(
      '#title' => t('Articlas'),
      '#type' => 'select',
      '#options' => $options,
      '#access' => 1,
      '#default_value' => $default_value,
      '#weight' => 1,
    );
  }
}
function getArticles($articleType,$vocabularyName) {
  //get the vocabulary
  $vocabulary = taxonomy_get_vocabularies();
  $vid = -1;
  foreach ($vocabulary as $item) {
    if ($item->name == $vocabularyName) {
      $vid = $item->vid;
    }
  }
  if ($vid != -1) {
    //get the parrent Term
    $query = new EntityFieldQuery;
    $result = $query
      ->entityCondition('entity_type', 'taxonomy_term')
      ->propertyCondition('name', $articleType)
      ->propertyCondition('vid', $vid)
      ->execute();
    $parrent_tid = array_shift($result['taxonomy_term'])->tid;
    //return children
    return taxonomy_get_children($parrent_tid);
  }
  return NULL;
}

Answer 2

According to this answer on the main Stackoverflow site, a submodule of Content Taxonomy called "Content Taxonomy Options"would be perfect for this:

You can do this with Content Taxonomy's Content Taxonomy Options module. Add a new Content Taxonomy field, and use the Select widget. In the field settings, under the Advanced settings for hierarchical vocabularies field group, select the Parent Term you want to use for that field.

Answer 3

The Term Reference Tree module might help. This module provides an expandable tree widget for the Taxonomy Term Reference field in Drupal 7.

Term Reference Tree:

This module provides an expandable tree widget for the Taxonomy Term Reference field in Drupal 7. This widget is intended to serve as a replacement for Drupal's core Taxonomy Term Reference widget, which is a flat list of radio buttons or checkboxes and not necessarily fit for medium to large taxonomy trees.

How to use this module

1) Enable the Term Reference Tree module.
2) Go to the Manage Fields tab of any fieldable entity (such as a content type, taxonomy term, or user.
3) Add a new field with a type of Term Reference.
4) In the widget select box, select Term reference tree.

5) Last step is important onc, as shown in the below image you have to give the taxonomy term id of which vocabulary you want to show for specific content type.

Answer 4

Mobile and Laptop should be separate Vocabularies.

Then for mobile content type, when you add a tax term field, select mobile as your vocabulary.

Answer 5

I would suggest avoding taxonomy altogether and define your own content types. I go into this in depth in another post. When you scroll down my post, you will find that you can do exactly what you are looking to do.

I am not a big fan of the "there's a module for that" philosophy because every time you add another module, you increase the footprint of your Drupal site; you load that module for ever page in ever session whether you need it or not.

By using Views, Entity, Entity-Reference, Entity-Connect (stuff you should be using) you can turn off taxonomy completely and get a better indexed alternative to taxonomy.

Say no to taxonomy