Get value of programmatically (form_alter) added fields at form submit

Question

I'm altering a node creation form using the form_alter hook in a custom module. In this particular case, I'm adding an email field which is not part of the content type structure. At the node creation, I need to send an email to the address entered in the field. Using the hook entity_presave or entity_insert I have access to the entity field that are part of its structure, but not to the programmatically added email field. How can I get that value at the form submit?

Answer 1

A field added in the form_alter hook is not created on the entity. Therefore you cannot retrieve the value in either hook_entity_presave or hook_entity_insert.

What you want however you can do by creating an additional submit handler for the form.

function _MODULE_NAME_custom_submit_handler($form, FormStateInterface $form_state) {
  $email = $form_state->getValue('email_field_name');
  // send email.
}

You can also get the saved entity (which does not have the email field) using $form_state->getFormObject();

Answer 2

So you added this MY_EMAIL_FIELD to the form with form_alter. Add the following as well:

$form['actions']['submit']['#submit'][] = 'MYMODULE_node_form_send_email';

Add another function to your file:

function MYMODULE_node_form_send_email($form, FormStateInterface $form_state) {
  $email = $form_state->getValue('MY_EMAIL_FIELD'); 
  // send email here
}

In this way, the email data won't get lost and you are able to send the email to the correct address.