I have a form that allows users to upload a CSV file. Upon submit, I would like to show a confirmation form ("Are you sure you want to import this file?").

However, the Drupal 8 examples for ConfirmFormBase seem to only focus on building the confirmation form without actually showing how one gets to that form from another form.

Can someone provide an example of a regular form that then works in conjunction with a confirmation form?


As you've already discovered, ConfigFormBase just provides some buttons, handling for messages, and submit/cancel logic. On its own, it's not designed to be used as the sort of multistep form you're looking for.

Getting that functionality is pretty easy though; you could use the logic in Drupal\config\Form\ConfigSingleImportForm as a rough example. Basically you just handle the multistep part of it yourself. For example:

protected $step = 1;

public function buildForm(array $form, FormStateInterface $form_state) {
  // When this is the confirmation step fall through to the confirmation form.
  if ($this->step === 2) {
    return parent::buildForm($form, $form_state);

  // Build and return your upload form as normal, but don't call the parent method.

public function validateForm(array &$form, FormStateInterface $form_state) {
  // The confirmation step needs no additional validation.
  if ($this->step === 2) {

  // Perform any additional validation 

public function submitForm(array &$form, FormStateInterface $form_state) {
  if ($this->step === 1) {
    $this->step = 2;

  // Extract rows from CSV and set batch to import here
  • I tried implementing this, but I ran into problem in the submitForm function in step 2, $form_state did not have the values saved anymore from the step 1 form. I fixed this by adding this line in submitForm after line $this->step = 2;: $this->data = $form_state->getValues(); That way, in step 2 you can use $this->data to reference all the values from step 1. – Risse Jan 19 at 8:47

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