'textarea', '#title' => $this->t('Message'), '#required' => TRUE, ]; $form['actions'] = [ '#type' => 'actions', ]; $form['actions']['submit'] = [ '#type' => 'submit', '#value' => $this->t('Send'), ]; return $form; } /** * {@inheritdoc} */ public function validateForm(array &$form, FormStateInterface $form_state) { if (mb_strlen($form_state->getValue('message')) < 10) { $form_state->setErrorByName('name', $this->t('Message should be at least 10 characters.')); } } /** * {@inheritdoc} */ public function submitForm(array &$form, FormStateInterface $form_state) { $this->messenger()->addStatus($this->t('The message has been sent.')); $form_state->setRedirect(''); } }