How can i programmatically get the value of a views exposed filter after the user submits the form?

Question

I've searched and cant find an answer to this specific question.

If I have a view and an exposed filter for that view in a block, when the user clicks submit on the exposed filter form, how can I get the values of the exposed filters in order to use the value elsewhere for a different purpose? For example saving the value of one of the exposed filters into private temp store for use later.

What hook can i use that is called when the user clicks submit on the exposed filter form? The only information I can find is regarding hooks that are called when the view is being built.

Or am i approcahing this wrong and should I be looking into the form submit function for the exposed filters form?

Answer 1

You want to add a submit handler to your exposed form

function HOOK_form_views_exposed_form_alter(&$form, \Drupal\Core\Form\FormStateInterface $form_state, $form_id) {

    array_unshift($form['#submit'], '_my_exposed_form_submit');
}

function _my_exposed_form_submit(&$form, 
   \Drupal\Core\Form\FormStateInterface $form_state) {

   $values = $form_state->getValues();