Update $form based on $form_state

Question

Shouldn't the form generating function get executed every time the form is rendered? Because I need to update some field suffixes based on the $form_state values and I don't know how to do this.

I have something like this:

function xxxx_some_form($form, &$form_state){
  $form["some_field"] = array(
    "#type" => "textfield",
    "#required" => true,
    // bla bla bla
  );
  drupal_set_message("whatever");
  $form["actions"]["do_action"] = array(
    "#type" => "submit",
    "#value" => t("Do action"),
  );
  return $form;
}

When I submit the form, the validation messages are displayed ( Eg: X field is required ) but the message from drupal_set_message("whatever") is not displayed.

Also, no other logic is executed there.

Answer 1

When a form has a validation error, the form is rebuilt from cache, meaning that the form function isn't invoked.

I could move the drupal_set_message call over to a #process or #preprocess function on the form itself or on one of the methods. These should be called again.

If the form is displayed with hook_menu you could also make a callback function which calls drupal_set_message and then fetches the form. There are a lot of ways to get around this.

Answer 2

Are you trying to get the form to be interactive? Have you looked at the #states ability of the form which lets you set up conditional display of other fields, markdown elements, etc?

Field suffixes sounds like a very weird thing to modify on form submission, since the expectation with a submission is that the user is now done with the form. And as for the messages, it is possible the template for the page you are working with does not have the message print lines.