How do I alter the submit function?

Question

I want to do array_unshift for submit function in D8. Array_unshift working perfectly for validate function but not submit function. Below is my code:

function example_form_alter(&$form, \Drupal\Core\Form\FormStateInterface $form_state, $form_id) {
  if ($form_id == "commerce_order_default_edit_form") {
    array_unshift($form['#validate'], 'example_manual_validate');
    array_unshift($form['#submit'], 'example_manual_submit');
  }
}
function example_manual_validate(&$form, \Drupal\Core\Form\FormStateInterface &$form_state) {
  $values = $form_state->getValues();
  dsm($values);
}

function example_manual_submit(&$form, \Drupal\Core\Form\FormStateInterface &$form_state) {
  $values = $form_state->getValues();
  dsm($values);
}

Answer 1

Here am altering the submit handler of the article content type while creating new article type contents

  /**
     * Implements hook_form_alter().
     */
    function example_module_form_alter(&$form, FormStateInterface $form_state,$form_id) {
   // dsm($form_id);

      switch ($form_id) {

        case 'node_article_form':      // New article nodes.
        // Attach our custom submit handler.
     array_unshift( $form['actions']['publish']['#submit'], 'example_module_node_article_form_submit');
          break;

      }

    }

    function example_module_node_article_form_submit($form, FormStateInterface $form_state) {
      drupal_set_message('custom submit ...');
    }

Source

Answer 2

Found Solution to alter submit function in D8 , this will be helpful https://www.drupal.org/node/2637958

function mymodule_form_node_form_alter(&$form, FormStateInterface $form_state) {
    foreach (array_keys($form['actions']) as $action) {
      if ($action != 'preview' && isset($form['actions'][$action]['#type']) && $form['actions'][$action]['#type'] === 'submit') {
        $form['actions'][$action]['#submit'][] = 'mymodule_node_form_submit';
      }
    }
}
function mymodule_node_form_submit($form, FormStateInterface $form_state) {
   $node = $form_state->getFormObject()->getEntity();
  // mymodule_do_something($node);
 \Drupal::logger(' mymodule')->notice('mymodule submit ') ;

}