I will try to be as specific as possible.

I have a required text plain field in a content type, say 'field_A'. This will have values of minimum 2 words, maximum 5 words. Words will be separated by spaces. I can be certain of this.

What I want, is to have another field, say 'field_B' in which I want to keep the last word of field_A. I would like this to happen automatically (upon creation of a node of this type).

I have no idea if this is possible ...

So, say I 'm adding new content of this type, and use value "lorem ipsum whatever" for field_A, upon submitting I would like the word 'whatever' to be inserted as a value in field_B.

I 'd be grateful of any help .. I couldn't find relevant info on this, it's kinda hard to describe in a few words.

Working on D8.

1 Answer 1


You probably need a custom module for this.

Add MODULENAME directory inside your modules directory. Inside the directroy create file MODULENAME.info.yml with contents:

name: Last word copy
description: 'gets last word from field_a and saves it to field_b'
core: 8.x
type: module
  - node

This module implements hook_form_alter that will make field_b readonly / disabled and hook_entity_presave which will get the last word added to field_b upon save or update of a node of CONTENTTYPE

Create also MODULENAME.module file with contents:

function MODULENAME_form_alter(&$form, &$form_state, $form_id) { 
  if(in_array($form_id,['node_CONTENTTYPE_form','node_CONTENTTYPE_edit_form'])) {
    $form['field_b']['#disabled'] = 'disabled';

function MODULENAME_entity_presave(Drupal\Core\Entity\EntityInterface $entity) {  
  if($entity->bundle() == "CONTENTTYPE"){    
    $pieces = explode(' ', $entity->field_a->value);
    $last_word = array_pop($pieces);
    $entity->field_b->value = $last_word;
    //save is done automatically

You NEED to replace MODULENAME and CONTENTTYPE in the above code.

If all is correct go to Extend (admin/modules) and enable the module.

  • thanks a lot for your info. I haven't created any custom modules yet - I 'm fairly new to drupal. But I will look into that. I thought it might be possible through preprocess functions, or any other (fairly simple) way. But still, your contribution is invaluable.
    – thomas
    Commented Apr 4, 2018 at 11:46
  • Added more specific instructions on how to create this module
    – GiorgosK
    Commented Apr 4, 2018 at 12:15
  • It does work my friend. I just tried it. Really helpful, and very well explained and given. Thanks a lot. I will research these hook functions, they can clearly be extremely useful .. If you can point to any good starting point for documentation and/or tutorials, please do.
    – thomas
    Commented Apr 4, 2018 at 19:42
  • 1
    In Drupal 8 You can exclude the form_alter() hook and just remove the field from the form display in the UI under Manage form display for the entity type.
    – sonfd
    Commented Apr 4, 2018 at 20:35
  • 1
    title/label has special way to get the value $entity->label() ... perhaps you should spend some time setting up a development environment for yourself drupal.stackexchange.com/questions/259037/…
    – GiorgosK
    Commented Apr 5, 2018 at 10:26

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