I need to create #states conditions between either the fields in any one element in a webform or across other elements in the same form. I'd hoped I could do it via the WF yaml editor but it seems I couldn't [1]. As per @jrockowitz 's comment on the attached link #1, I

might be able to use a form alter hook to add the needed #states

I am not a developer but it seems with drupal 8+ I do need to learn to start to be one and that's on my list for sure. I'd love to be able to contribute something to Drupal and especially webform but I find the learning process intimidating especially with the lack of "beginner-type" tutorials at least when it comes to creating custom modules with more than "hello world!".

For now, I need to know the steps I need to follow @jrockowitz 's advice and use hook_form_alter to serve my goal. My understanding is that could be done either on a theme level or custom module level (please correct me if wrong) and since I'm more comfortable with the theme way and I feel it's simpler for someone like me, I like to know (at least):

  1. which files ( other than MYTHEME.theme) I need to edit or/and create to start with and
  2. what info do I need to look for and study so I can do the job and begin my learning journey.
  3. I learn best by example and so any extra clear a-b-c type tips to get me started is greatly valued if any.

If the custom module way is more advisable or the only way:

  1. What is the minimal skeleton of a custom module that I need to have for the purpose.
  2. What do I need to study to learn how to create such a module.

(I'm not sure if the last question should be a separate question so please forgive my newbie status here but I promise I've done my best)

Thanks so much everyone

A sample of what I want to achieve:

  '#type': tableselect
  '#title': 'some question'
    q1: 'q1 (hide if q2 is checked)'
    q2: 'q2 (hide if q1 is checked)'
    q3: q3
    q4: q4
    q5: q5
    q6: q6
    q7: q7

Related links:

[1] Why isn't my custom Form API #states applied in my webform yaml editor working?

[2] https://api.drupal.org/api/drupal/core%21lib%21Drupal%21Core%21Form%21form.api.php/function/hook_form_alter/8.7.x

[3] https://www.jrockowitz.com/blog/add-ons

  • Before heading to custom dev, can't your goal be achieved directly from your Webform admin interface with webform field conditions?
    – misterdidi
    Commented Jun 20, 2019 at 8:16
  • @misterdidi thanks for your comment. I'd love to start learning custom dev for more than a reason but for now, unfortunately, it seems no I cannot do it via the UI like I stated in my post according to my other question which led me to this q. drupal.stackexchange.com/questions/282349/…
    – Adam888
    Commented Jun 20, 2019 at 10:22

1 Answer 1


Ok, if you need to rely on custom dev, you can indeed use hook_form_alter().

It would work if you set it in your mytheme.theme file but for unrelated theme issues I prefer to rely on custom modules. To create your module:

  • Create a mymodule.info.yml file in the folder /modules/custom/mymodule of your Drupal website. See this page for providing your file with the minimal content to have your module detected by Drupal.
  • With only this file you should be able to enable your module
  • Create a mymodule.module file at the same level as your .info.yml file
  • In your .module file (or mytheme.theme if you chose not to create a module), add the following:
function mymodule_form_alter(&$form, &$form_state, $form_id) {
  // Target your form
  if($form_id == "your_form_id") {
    // Use Devel Kint module to display the architecture of your form and make it easier for you to find the elements you wish to alter
    // Now you can access the elements of your form and edit the desired ones

    // Hide checkbox "my_checkbox_name" if checkbox "my_other_checkbox" is checked
    $form['my_checkbox_name']['#states'] = array(
      'invisible' => array(
        ':input[name="my_other_checkbox"]' => array('checked' => TRUE),
    // Make field "some_input_text" required if input field "some_other_input" is filled with value 'hello'
    $form['some_input_text']['#states'] = array(
      'required' => array(
        ':input[name="some_other_input"]' => array('value' => 'hello'),

I recommend you to have a look at this page for the list of available #states and some examples as well.

Happy coding!

  • wow! just that ?! I thought more files would be needed. Thanks so so much for your kind help and clear answer. I can't wait to try it and update you with my results
    – Adam888
    Commented Jun 20, 2019 at 14:17
  • sorry for being months late. I managed to create the custom module and made sure it's working but the function in your answer unfortunately isn't working. The form_id I'm using is correct afaik (I tested with an echo call and it's attaching) and the checkboxes names correct too. Any ideas ?
    – Adam888
    Commented Feb 15, 2020 at 7:06
  • If your $form_id is correct, then I guess the issue comes from the #states code. Make sure that you are targeting the right element from the $form array (for instance, I have webforms where my fields are stored in an "elements" array). So my code would end up with $form['elements']['my_checkbox_name']['#states'] = array(...); Sorry if I can't help you more but it's difficult for me without knowing the structure of your form and having a look at your hook_form_alter().
    – misterdidi
    Commented Feb 18, 2020 at 8:51
  • Thanks a lot @misterdidi . I'd actually given up the whole hook_form_alter way and re did the questions involved as separate elements so I could set their states via the built-in conditions manager. I still love to figure this out and find the culprit. I edited the question and added at the end a sample to illustrate the type of element and what I want to achieve if that may help. Otherwise, I appreciate all the help and I'm going to accept your answer since it indeed answers the essence of my question and helped me with my first custom module.
    – Adam888
    Commented Feb 19, 2020 at 1:54
  • @Adam888: If I understand the sample you added, you actually wanted to alter the options of an element depending on its own options values, right? As far as I know it is not something you can handle with #states (#states listens to the other form elements, but cannot listen on the very element it is set). Instead, I would use custom Javascript to achieve what you're looking for.
    – misterdidi
    Commented Feb 24, 2020 at 14:26

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